I’m not sure it’s a bug actually, more likely a really overly aggressive forward compilation. With ODSC instead, now when I open a folder for the first time, a handful of shaders get queued on the spot for compilation, as the Content Drawer has its display constructed little by little. So most likely most of the stuff that gets compiled in those 10K+ shaders is for this kind of display, or the displays when editing materials, maybe for each of the possible display shapes in there, etc.
I’m guessing the engine content is included in this operation. I don’t have time to test right now, but one thing you could do is to try and move any unused content out of the Engine\Content itself (as well as from your projects).