1. The evolution of the .270 is well documented in ...
2. Where they got the inspiration is anybody's guess, but there have been many cases of parallel evolution in rifle cartridges.
ad 1. Unfortunately I know many cartridge "documentations" you and I would call "crap". Especially of US origin - just give COTW a look) where facts from Europe had "not very much" influence (to put it mildly).
ad 2. You are right, there is a lot of parallel evolution in cartridges.
But please remember that the .270 Win. bullet diameter is verrry close to metric 7 mm....
