It's not fully mitigated by encryption, you can still do a lot of damage without being able to observe plaintexts. For example, you could "rewind" a ciphertext block to an earlier value, and induce a UAF-like condition in the software it belongs to.
Apple’s Secure Enclave has replay protection since Apple A11.
Generally, I don’t see why a modern security platform wouldn’t have its own private SRAM to be used as a root of trust for encrypted blobs stored in shared DRAM.
