I appreciate and understand that the fan on this SBC is controlled by an embedded controller and temperature sensor other than what is built in to the main CPU chip. That is a reasonable engineering choice made by the SBC designer. However, it does not seem to be working very well. I too put this SBC through the same stress test and it got quite warm. The fan remained quiet. In the BIOS the fan speed shown is highly erratic and unpredictable. When the SBC is warm the fan speed reported in the BIOS will jump around erratically from zero to over 9,000 RPM back and forth in seconds. The fan is not doing that - it’s just what is reported on the BIOS screen.
For the record, mine has the 64GB eMMC and came with Windows 10 installed. I activated the installation with a legally obtained Windows 10 Pro code.