The tag merges done were for synonyms. Not for stuff being similar. Have you seen any examples for merges that were not mere synonyms or different spelling? In the thread you linked I could not find any.
From your suggestions, endless + infinity runners seem to be synonyms and could be merged. Maybe others, I did not scrutinze everything.
For contrast, a wordle is not a crossword puzzle. Dark Fantasy is not of the horror genre. While webcomics are comics, comics are not webcomis, even if you sell them on the web. As for splitting, you are right, non-linear does not say much, if used alone. But that is why you have 10 tags and 1 genre. It is the combination. Just like an example in the merge thread: puzzle + endless. It is usage of both tags that give meaning.
That this list is called "all" tags, is bugging me too. It should be called suggested tags or something like that.
Edit: I just checked, the "merges" are done with aliases. As long as they use the word alias for this mechanic, I would assume they will only "merge" synonyms and different spellings.