Presumably as part of the generative AI stuff they crammed into it? They've been hilariously cagey about the details here which makes me think it has to be AI-feature related
Not sure what you think is "hilariously cagey", but why would they only be "cagey" if the bug was from ai-features?
Also it says paint versions are "affected from 11.0.0.0 before 11.2605.91.0" which I take to mean the bug has been there since Windows 11 was released in 2021