Interesting link, thanks, I wasn't aware of that. The link seems to suggest that the odd mixed-endian string representation ("Variant 2") is now quite rare.

With the one that's more common ("Variant 1"), I'd say that I *slightly* disagree that representing the byte sequence 99,aa,bb,cc as 99aabbcc is "big endian". If you don't philosphically think of the latter as a number, then it's just the bytes written out compactly. But I do see that if you think of it as a number then it's big endian, especially if you're distinguishing from variant 2.

Variant is a very abstract concept mostly for humans, programs pay no attention to it and serialize all kinds of UUID the same way.