Remembering is not an action
Beholding a creature and trying to recall information about it would not take an action. Perhaps it might be considered "interacting with an object or feature of the environment" (PH 190) - which a character can do once on its turn without expending an action.
But there's another way to preserve a little mystery about your monsters…
Explanations are actions
If one character recalls the creature, that doesn't mean all characters have. You could slip a note to the character(s) who succeed the knowledge check. If they share more than "brief utterances and gestures" (PH 190) about the monsters, then it's rules-as-written to determine the character spent its action.
Player Knowledge vs Character Knowledge
If you've got power gamers at your table, it's also reasonable to insist the players don't abuse player knowledge. If the players have the MM memorized, and a player shares the monster's name, you can rule that the character spent its action giving the characters the knowledge the players already have.
(Alternatively, just change details about the published monsters yourself.)
I think that neither yourself nor your players, are playing Numenera. Warning signs such as "dungeon-making skills" and characters able to use 5 level of effort (wow!) makes me think that you are trying to play D&D with a different world and system. This will not work, as you clearly found out. This is an paradigm problem.
In any case, the true path to Power in the Cypher system is, well, the cyphers.
The whole point of Numenera is to use cyphers like they went out of fashion. After all, you gain many new ones all the time. Traditional hoarding will hold you back and make you less powerful. This needs to be clearly explained to the players: "Do not hoard, spend!"
So, do a silly one off encounter with different cyphers: each player plays their character but with a random set of cyphers. The aim is to defeat the obstacles in their path using those cyphers. The next iteration has new cyphers so forces the players to adapt. This should not take more than an hour per round. Do a few, and your players (and yourself) will get how it work. The aim here is not to defeat all the obstacles, it is to get used to spending cyphers. It should forces the players to think outside the box and come up with new and fun uses for their cyphers.
A good such encounter might be a physical fortress, a hostile guardian, some social interactions, and a combat against people using the same cyphers themselves in each iteration.
During game play, offer them many new and interesting cyphers. So, unless they use theirs, they cannot pick up the new ones. Sure, they can discard some to pick a new one but really, where is the fun in that? You are not playing a tactical board game (neither sarcasm nor insult implied) but a story game. Make sure you players know that their characters are not going to die because they spend that cypher last session.
If the players have a healing cypher (say it regenerates limbs), then clearly your next GM intervention cuts a character's hand. Said player can either take it, gleefully get a XP, and regrow a limb or be boring. Now, of course, another GM intervention that turn said arm into an obsidian black animated sculpture might work well -- think Hell Boy.
As a GM, you know what cyphers they have. Suggest to them to use them: "Alice, your character has a cypher that allows her to float. That might be a good way to get your bearings in this weird wood."
Finally, you need to talk to your players and convey the idea that they are responsible for building the world around them as much as yourself. Cyphers are one way to make it the commonly shared story more interesting.
Best Answer
However your table wants
Yes, it's usual and yes, it's common. And unless you poll every group that's ever played (or at least a statistically significant sample - PhD anyone?) you won't know which is more frequent. Look, some people like to create deep and complex worlds where each session is a new revelation and some people just like to chop things into mincemeat - you do you, ok.
Metagaming
I hate that word.
For a start it has two meanings:
The game about the game. Looking at the character classes and choosing to play a ranger rather than a wizard is a metagame decision; just like a coach watching video of their opponent in this week's football match and consequently adjusting strategy is metagaimg. This usage is not problematic and is usually not what's meant when a role-playing gamer uses the term.
Particularly in a role-playing game; it's applying knowledge that the player has that the character ostensibly doesn't have. It's this usage that is problematic and I will now indulge in a short rant because the concept sets my teeth on edge.
Its a game of make-believe elves in a made-up world using rules that cannot be anything but the most abstract model of non-reality!
I cannot for the life of me see that rolling a d20 to see if you "hit" is not metagaming1 but claiming that your character, who supposedly grew up in a world where vampires are real, knows that sunlight hurts them isn't. Hell, vampires aren't real in this world but everyone knows your best defense is a garlic-wrapped wooden stake!
OK. Rant over.
Basically, it's offensive metagaming if it breaks your table's verisimilitude and it's ok metagaming if it doesn't. So, you and the people you play with need to set your own boundaries on this, just like you need to decide how naked you can be while you play.
Options
Of course, you can and should mix and match - trolls are common so everyone knows about fire, but kdsja2 are rare, so only the most arcane tomes and learned sages know about their vulnerability to tulip bulbs.
1In the second sense - it clearly isn't in the first sense because that is the game.
2Don't bother looking for kdsja, I just made them up.