I wouldn't be surprised if the ARM builds don't require a TPM, and they kick the can down the road WRT requiring equivalent functionality on ARM. TPMs are very, very x86. For instance that LPC bus they sit on is almost electrically the 8086 front side bus, just with a tiny state machine in front to serialize it (hence LPC: Low Pin Count 8086 Bus).

There's of course equivalent security processors and domains on pretty much every ARM application soc, but the exact semantics of them (like pretty much everything in the ARM space that's outside of the actual CPU core complexes) is extremely heterogeneous. They might even be running in EL3 on the application cores themselves. Wrangling all of that is probably out of scope for W11 RTM.