Well, first, we don't have enough context to judge what the "load-bearing seam" was used for in this case ("The key structural point first: the only load-bearing seam is [...]"), so we don't know if it was meant in the well-defined legacy-code sense. But that doesn't really matter.

I'm taking issue with the combination "load-bearing seam". It's a bad metaphor, because seams are usually structural weak points in the physical world, and not load-bearing in the sense that this modifier is usually used. (Seams need to bear loads and stresses to do their job, but so do walls; yet, we do not call all walls load-bearing. We mean something extra when we say that, something that seams don't do.) Even if we were talking about seams in the well-defined software sense, as opposed to the metaphorical one, you still get a mixed metaphor as a result that I find extremely awkward and grating. It doesn't have to be. There are so many ways to highlight the importance of something without calling it "load-bearing".

I understand that you don't see it that way or don't care, but to me, the result is thoughtless, careless and vapid. Bad metaphors put little holes into a text, they leave eddies of confusion where meaning should be, they look load-bearing while actually being weakening, they're like a fart in the elevator that should lift the reader's understanding.

Note that I'm not calling into question that seams may be well-defined in some software contexts, or that "seam" and "load-bearing" can be valid metaphors on their own, as you describe. I think you might have misunderstood me that way. I'm only calling out, and fed up with, the bad style that permeates LLM-generated prose like the whiff of something not quite digested.

It's not this particular case that irks me, but what it exemplifies. I wouldn't mind so much if similar things to this weren't there everywhere, every single day.

If it doesn't bother you, I'm happy for you.