ThinkPad X1 Carbon Gen 4 unable to boot 13.0-RC1

[Fred Hall]

I have a ThinkPad X1 Carbon Gen 4 (20FCS0NB00) which has happily run FreeBSD 11 and 12, but which can't boot 13.0-RC1 from memstick or via freebsd-update. In both cases the boot process locks up on the line "hwpstate_intel0: <Intel Speed Shift> on cpu0"
If running freebsd-update, a work around is to add hint.hwpstate_intel.0.disabled="1" in loader.conf. See the note under the Eighth Generation (2020) in https://wiki.freebsd.org/Laptops/Thinkpad_X1_Carbon
I was quite surprised to find the lack of support for hwpstate_intel in 13 when it apparently worked under 11 and 12. Does anyone know the status of hwpstate_intel on ThinkPads?
Cheers, 
Fred