Actually in this specific case it wasn’t even that…

The good news is that Griffiths managed to save the player’s, uh, save. In a further update, he posts a video of the game running flicker-free in the same area on the same save. Per Griffiths, the problem was a “general engine bug/limit being reached,” which means that his fix will “probably help other large bases that had this issue on Xbox.”

The save helped with it, exactly like I’ve been saying this whole time.