Yeah, the reason for that is that it's expensive in PPA for the size of an L1 cache to exceed number of ways times page size. The jump to 48kB was also a jump to 12 way set associative.

As an aside, zen 1 did actually have a 64kB (and only 4 way!) L1I cache, but changed to the page size times way count restriction with zen 2, reducing the L1 size by half.

You can also see this on the apple side, where their giant 192kB caches L1I are 12 ways with a 16kB page size.