That's not because of language evolving with the need for same thing from different places or nickname that's grown out of a subgroup. It's by design, kbin (afaik) is a fork of Lemmy and decided they want to use a different name - maybe because they wanted to differentiate themselves from Lemmy, I'm not sure actually why. Certainly they didn't take into account both Lemmy and kbin growing side by side both profiting from other's success. Either way, it's a failure of design for the fediverse, time will tell if it actually matters though.
(You can sure argue language works by assigning word to describe thing but usually it's meant that meanings can grow and change with time with the population.)
And I'd argue sublemmy thing is a thing at all because community-magazine thing isn't that obvious. You never heard anyone in Reddit call them anything else than subreddits or subs.