TL;DR: I removed the ambiguously mac-os tag and grouped classic stuff under mac-os-classic.
I first came into this tag seeing a ton of osx questions so I wrongly assumed mac-os meant osx and it didn't came to my mind that
X actually stands for 10+ here. So, then I went to tag them mac-os-8 and mac-os-9. But, that was also messy.
So, I went on to retag Mac hardware questions to mac, 0-9 to mac-os-classic and 10+ to osx.
The reason I wanted to get gone of the 10-15 questions in mac-os is because that tag is ambiguous, at least half of the questions were actually osx questions which makes the tag less valuable.
The other thing that might be bothering is that mac-os-classic and osx are inconsistently named, using os-classic might make no sense though. Using mac-os-x doesn't either, because then you are going to have issues having long tags like mac-os-x-snow-leopard.
Note that I did most of this tagging before this meta question came, which mods allow us for tags that contain a very low amount of questions and that would make sense to retag. Glad DL catched my error.