Can't you still go through the song and dance of disabling SIP and authenticated root and then editing the root snapshot? It's incredibly annoying but should still work, right?

Generally things don’t like it very much when I lie to them about what OS they’re running on; I try to set the version just before opening Xcode and fix it then right after I’m done submitting the app so my computer isn’t confused. More than once that has been long enough for Software Update to get confused and offer me a new build :P