Unfortunately I cannot say that either

I bought the repeater (also CH version) to go with the Fritzbox (CH version). Both work perfectly together on a Swisscom fibre optic connection. I would assume that a different firmware version (i.e. without CH) (or a mix of versions) could cause problems under certain circumstances. One would then possibly be forced to exchange the firmware. But this is only a guess, to be on the safe side it is best to clarify this directly with Fritz Support.