I had another thought based on your question about other monitoring programs. The Taichi has two 7-segment displays onboard for diagnostics and I had configured the bios to show Tdie temp on those. All readings have been normal for almost 24h after disabling that monitoring. Maybe that was...
So I have tried now for 20h without Afterburner running. I updated HWInfo from 6.24-4120 to 6.26-4160 and here is the same readings. It might be worth noting that my Gigabyte X570 does not have this problem, only the Taichi.
I'd like to report similar behaviour on an AsRock x470 Taichi. This has been an issue across several versions of HWinfo64. The only other "monitoring" program I run is MSI Afterburner.