Thanks a lot for the provided info. Could you also collect the tech report please? Please collect the tech report right after the issue reproduced and post the repost's ID here.
Can you confirm that host mac is also not clocking down via Intel Power Gadget? If it isn't, your issue may be the same as https://forum.parallels.com/threads/strange-cpu-behaviour-high-clock-speed-low-utilisation.345190/
