I think it's more a matter of expertise/experience than size. The different platform teams have to have gelled enough to agree on the core architectural abstrac

I think it's more a matter of expertise/experience than size. The different platform teams have to have gelled enough to agree on the core architectural abstractions, which is a level of maturity that goes a step beyond necessity. So the platform teams need to have shared prior knowledge of how to build with the same architectural patterns, and they need to be sold on the possibility and merits of using those same patterns and coordinating on their plans of implementation.