kodi fork versions of 17.1

i was asked this and was not 100% sure of the answer… This might be a stupid question but I’m gonna ask it anyway, if they can make fork versions of 17.1 to run on 4.4 boxes why can’t kodi make 17.1 run on 4.4? because the fork versions are exactly the same and run better.
i thought it was something like this… tbh im not 100% sure,but i think kodi developed the code for api above 19 and several python codes
can you tell me more clearly please?
tbh i have not seen a fork of 17.1 just 17.0