If one compares body size of early Sony APS-C cameras (NEX-5, a5100, even a6000), to the newer models (a6400, to ignore OIS models), the difference is staggering.

Size is approaching full frame models like 7M2. But yes, lens is where it baloons further, yet good all-purpose zooms are chunky for APS-C too. I sometimes carry multiple cheaper primes on several bodies because that's easier to pack.

So really, body sizes have grown due to processing and cooling needs (and in-camera OIS), but lenses still bring more heft (even with FF: look at the size of A7C series).