I have found several inconsistencies regarding tag synonyms. For example take the iOS tag: https://apple.stackexchange.com/tags/ios/synonyms
The synonyms are: ios4 ios4.2 ios3 ios5 ios-5.1 ios7 ios-7.1 ios8 ios9 ios10 ios-beta ios-8 ios-9 ios-11 ios-10
Also take the WatchOS tag: https://apple.stackexchange.com/tags/watchos/synonyms
The only synonym is watchos-3. Another inconsistency there as well. Surely there should be synonyms for all versions 1 - 5. But I support making them separate tag verisons as said below.
Individual tags for iOS and WatchOS versions
There are a lot of inconstancies there. For example there is a tag called iOS 7.1 but not iOS 10.1. Also I am finding confusing why are we not making tags for individual iOS versions. I know there is an iOS 12 tag: https://apple.stackexchange.com/questions/tagged/ios12
Mac's have different tags relating to their versions for example sierra and Mojave. Why not do the same for iOS and WatchOS.
You see if a user is asking a question or is having an issue with a specific issue with a specific iOS version then it is much better to have it tagged with that version. If the feature is not available on other versions then it is a bit confusing.
Also it makes the post more accessible. If a user knows a lot an uses iOS 12 but has never used 11, it will be much more useful to him going to question knowing that he will be able to answer it and it will be about iOS 12. If they are synonyms then the user might waste his time going to an iOS 11 question, not being able to give an answer, but they could rather spend their time on helping people and not waste their time.