The x86_64 v1.13 23.09 SDK doesn’t work for me out of the box on a Fedora 39 system using QEMU v8.1.1. Attempting to boot the VxWorks kernel with QEMU just results in QEMU using 100% CPU time and hanging until forcibly terminated (via ^C), with no output ever shown.
The previous x86_64 v1.12.1 23.03 SDK works just fine, as do all previous SDK versions going way back through the archives.
While I didn’t try QEMU v8.1.2 (the current version), I did build the older QEMU v7.2.6 from sources, and this worked – so you need an old QEMU version with the new SDKs, but the new QEMU works with old SDKs.
Since that’s rather non-intuitive, I assume it’s a bug and not intended behavior.