I would say, that 25,000 is an obsolete number. It was written long ago; since then, we only increased the available options
(But I have no actual number myself, just a thought.)
And no, there are not OS settings. These are only things that can appear in registrymodifications.xcu
. I think that whoever counted them, didn’t try to count unknown settings of third-party extensions (that of course would add to the count). And yes, when I repeat, that this is a complex software, and that it is simply impossible to test all combinations (multiplied by infinite number of possible document situations), I really mean it 