[sedatk]

Okay, I had assumed JIT for x64 wasn't possible (yet) and ARM64EC enabled that partially. So, ARM64EC images are actually native ARM code that can interact with emulated (+JITted) components. For some reason, I thought native ARM64 binaries already had this capability, but they don't. Thanks, that's actually a better state of affairs in Windows on ARM land.

[agosz]

Yes, that's correct! Unfortunately ARM64 can't fully interface with x64 code (e.g. you can't translate an ARM64 CONTEXT to an x64 one directly due to differing numbers of registers), so the backwards compatibility is restricted to ARM64EC only.