That's not how cleric spellcasting works
While clerics know all the spells on their list, they can only prepare a certain number per day: (PHB 58)
You prepare the list of cleric spells that are available for you to cast, choosing from the cleric spell list. When you do so, choose a number of cleric spells equal to your Wisdom modifier + your cleric level (minimum of one spell).
However, domain spells don't count against your preparation limit (PHB 58):
Once you gain a domain spell, you always have it prepared, and it doesn’t count against the number of spells you can prepare each day.
Thus, getting these domain spells allows you to keep them in reserve while preparing other spells, increasing the variety of spells you can cast per day (but not the total number, which is limited by spell slots).
You're 100% correct that life domain clerics don't get spells from other spell lists, but I'd dispute whether that means they get the short end of the stick, for the reasons listed above.
Additionally, life domain clerics do get bonuses to their healing spells, both domain and non-domain, through their Disciple of Life and Blessed Healer features.
This is what the PHB says about scenarios that demonstrate one group surprising another:
A band of adventurers sneaks up on a bandit camp, springing from the trees to attack them. A gelatinous cube glides down a dungeon passage, unnoticed by the adventurers until the cube engulfs one of them. In these situations, one side of the battle gains surprise over the other.
So it's being shown to us that the encounter wherein creatures can be considered surprised begins when one group takes hostile action against the other group that has not noticed the first. And note that surprise can only happen when you are in the first round of the encounter, which means that, if you want to take advantage of surprise, Initiative cannot be rolled before the start of the ambush.
It also doesn't make sense to give someone the surprised status when nothing is surprising them (ie, the players are planning, not ambushing). When you are surprised, you cannot move. Does the act of the players planning somehow paralyze the other group? No, it shouldn't.
Best Answer
Druids choose their archetype at 2nd level, and Warlocks effectively have 2, 1 at 1st level, one at 3rd level, so there isn't really some universal rule that is being broken here. Archetypes are just another class feature, even if they are a particularly important one.
For that matter, the term archetype isn't even a game term. Fighters choose a "Martial Archetype", Rangers choose a "Ranger Archetype", and Rogues choose a "Roguish Archetype". None of the other classes even mention the word archetype. For example, the Barbarian chooses a Path, the Warlock chooses a Pact and a Patron, and so on.
This isn't a case of a general rule which spellcasting classes have an exception to; different classes get their features at different levels.