Not sure if it's a stated goal somewhere official but there's been plenty of fixes of the years moving stuff to be deterministic, e.g https://github.com/llvm/llvm-project/commit/cdbde3aacc1260a7...

The internal programming guide also says which collections to use for deterministic iteration order: https://llvm.org/docs/ProgrammersManual.html#llvm-adt-setvec...

So definitely a bug here.