Rosetta 2 is still supported, and the way Rosetta 2 works requires that various system components that x64 apps might depend on also be available in x64. x64 code that is running as arm64 translated by Rosetta 2 can’t call into native arm64 code due to ABI differences, so Rosetta 2 must translate the x64 version of system libraries as well.

My impression was that this did not require the kernel though, just system frameworks, so I don’t know why there’s a full x64 kernel in there!

Not saying this is the reason, but we build and test and release our software on platforms nobody uses, as it catches rare compiler / memory / UB bugs we otherwise wouldn’t have (eg win32 and FreeBSD)