Point by point comparison

Fate Core

• skill driven - characters competency is in specific fields of endeavor.
• Stress track increases from base with certain skills and certain stunts, thus not all are equally able to take stress
• Separate Physical and Mental stress tracks, plus optionally, Wealth, Magic, and Karma stress tracks.
• PC's by default start with one skill at Great (+4)
• 3 background related aspects. Plus up to 2 more of personal choice.
• Background created collaboratively
• 3-5 stunts

Fate Accelerated Edition

• approach driven - character competency is in how the task is approached, not in specific fields.
• Everyone has the same sized stress track and same number of consequence slots; everyone is thus equally able to take stress.
• one unified stress track.
• No PC starts better than good at anything.
• a high concept aspect, a trouble aspect, and 1-3 other aspects.
• No background required
• One stunt.

Implications

Fate Core

Fate core is somewhat grittier; characters are distinguished by skills and stunts as well as aspects, and can have widely different resistance to various kinds of stress. It's more "realistic" in that way. It's also more involved, and focuses on group collaboration.

Fate Accelerated

More cinematic. Characters differentiated primarily by their aspects and stunts, and are much more broadly competent, but less likely to be particularly skilled in any given area. Also, due to the ability to do character generation alone, the party need not generate together, so it's better for drop-in/drop-out campaigns and one-shots.

I think that the problem is conflating the hiding of relevant story related aspects and the hiding of the unknown.

Hiding the unknown is totally cool- in those two questions that you link (and one of them is mine), it involved hiding what the player was using, and what the player was rolling. That takes away player agency, and interferes with one of the tenets of Fate.

However, use of descriptions to convey dread and obfuscate the nature of an opponent- that is dealing with the unknown. As long as when that opponent intersects the player's agency they understand the nature of what they're dealing with, you're in clear territory.

To take an example: In one of my games, the bodyguard for the person that the PCs were trying to protect turned out to be working for the Big Bad. He had aspects that would point to his cover that were obvious, i.e. Disdain for his Charge. He also had aspects that were not as obvious that revealed his loyalties, i.e. Divided Loyalties. He also had abilities that were far outside of what a bodyguard should have- this is where the ladder and their descriptors come into play when describing his movements. Instead of saying that he used a Melee +5 to block the players attack, I instead say the total that they have to beat. Then when describing it, depending on how obvious I want to be about his abilities, I might say that "his defense was far above average- one of the most superb examples of wing chun that you have ever seen. Or for less obvious uses, I would just describe it.

The player has the agency to use his fate points as normal to overcome the DC. But they don't know whether I rolled well, the NPC was very skilled, the NPC used Fate points, or a combination of the three. But it does become obvious in the dialog that something is going on, and if they player wants to guess/use a skill/invoke an aspect, they have the information that they need to make it happen.

In this way you're able to maintain the air of mystique around the opposition, and in many cases, ratchet it up more than if you didn't give the information at all. After all, what you're really trying to engage is their imagination and their mind- this information sometimes makes them freak out more than just not knowing; I've seen it in action.