Yes, and this is exactly why it is bad:
it should not be a metagame stat, that decides which AC someone has!
But the hitpoints are ok?
How about number of spells, or save bonuses?
The games numbers are pretty arbitrary in most cases, and the level system is a way to both build and gauge relative threat. You either end up assigning high armour class to high levels, or building creatures "logically", and end up putting the ones with high armour class in the higher levels (which may mean re-jigging some other part of the creature design that "doesn't fit" with the assigned level, such as number of hit dice)
In the alleged flattened maths of 5E, AC won't in fact be a major factor related to level. I don't think that's anything to do with level being "metagame" and AC somehow being a more real thing.
I'd like to take the chance to rant against some minor mis-use of English common in these discussions; Level is
not a metagame stat. It's a game stat. As in, it is a number used in the game which has meaning in the game rules, and affects the outcome of the game. As such, the only difference with AC is that AC has some pretense of a relationship to character equipment and physical traits. Whereas level is more nebulous, related to concepts such as skill and threat. Being more nebulous or intangible does not in fact make something "meta"
A true metagame stat might be "the chance that our DM will actually use this creature, as written, in an adventure" . . .
I don't think the definition changes the terms of discussion here, just something that irks me
I guess when people call out level as a "metagame stat", what they are trying to say is that it is somehow OK to figure out the likely AC of an enemy (because it is encased in iron for example), but not to second-guess or figure out the relative level (because there is less to observe), or to use metagame logic to figure it out by assuming that the threat must match their characters. I don't necessarily agree, but I do see it would be annoying if you are trying to create an air of mystery around an encounter.