I think there is two issues here:
1. Presence of X-01 necessarily must be interpreted as "Bethesda broke the lore." I don't think this is the case. It has been 200 years since F01 (or was it FO2 where we learn of Enclave? anyway . . .) there are literally a thousand different explanations for how a technology that was developed 200 years ago and several thousand miles away (yes, even across a wasteland continent) might wind up in Natick, MA, sitting in some military installation.
Agree, the implication seems to b that many of those locations have sat idle since the day the bombs fell, but maybe that is a false assumption. Maybe the Enclave (or a nascent element of them, or an offshoot, or someone who stole their tech) was still operating in some of those installations a few decades after the Enclave developed the tech and that is why the suit 'could' be there.
You do not have to like any of these explanations, I don't like them myself. But in the absence of authoritative proof that these locations have definitely sat locked up and sealed since the day the bombs fell, you cannot fully discount such explanations. Its called "leaving it vague."
Bethesda might have been "sloppy" here but I don't think it reflects "arrogance" or a desire to poop on the lore. There are too many possible and unfalsified explanations for how these things might have wound up there in ways that would not breach the lore . . . to say nothing of the idea that the Enclave were just wrong/lying.
2. But then we have the second issue, and that is the 'random' or 'semi-random' spawning of these things depending on level. I confirmed it. Those guys are right, there is an element of random. This to me is the bigger 'breach' and I now see that it is tied with a related complaint that I've been cogitating on for some time and that is the way the random loot system works in general.
It makes absolutely no sense that a blood bug or a mole rat has a "legendary shot gun" or some other large heavy metal object "in it." What the hell, did it swallow it!?
They should patch the game so that legendary items do not spawn on smaller critters. I suppose Death claw _might_ conceivably swallow a whole chest plate or shotgun, but that still seems a bit unlikely.
The randomly spawning level-based power armor is obviously a related mechanic and I disagree with it. It had me fooled, and at LEAST the damn things do not respawn after you take on from a location (or morph into a higher tier one if you find it, leave it and come back), but now that I see how it is really working, I have to say I do not like it, especially for something as special as X-01 is intended to be.
I agree with Jaramr said up above: a quest with an Enclave hold out would've been much better. Is it really necessary or "good design" to have multiple suits in one play through!?