I think all you can do about this is complain to Apple and use Character Viewer or the ABC Extended keyboard instead.
Making a custom layout for the characters you need most often with Ukelele may also make sense. Or creating text replacements for them (for example using the hex codes as the triggers).
Update: Still broken as of MacOS 12.6
Update: Still broken as of MacOS 13.2
Update: FIXED AS OF MACOS 13.3
I think 256 codepoints are affected, but not all are occupied. This chart shows them: