This is the strange behaviour in my opinion.
The new rel is skipped and the old one reinstalled.
Maybe it’s due to an inconsistency in the paru cache as they mention, and you could try
rm -r ~/.cache/paru/clone/libidn11
As suggested.
Btw, do you really need this package?
It’s probably a dependency of steam-native-runtime, which has been recently deprecated from the Chaotic-AUR