I always believed that most of the showa spfx films were in the same timeline however the continuity was very flexible. E.G. KKE, there is the film as it happened but as far as the timeline is concerned, all you need to know is KK chills on an Island in the south pacific where he fought Gorosaurus (and possibly Mechani-Kong in Tokyo). The height discrepancies and specific story details are only pertinent to the film and not the over all showa timeline. Another example in Rodan, 2 Rodans are swallowed up by a volcano however in Ghidrah it was only acknowledged that there was only one Rodan. I am perfectly happy accepting the timeline that everything from 1954-1975 is all apart of one extremely loose, poorly connected timeline and try not to overthink it. (unlike people that try to connect all the showa, heisei and millennium films together)
I have almost nothing serious to add to any conversation ever.