I disagree. The fans are managed by the BIOS, and they behave wrongly. Faulty BIOS is the cause. Other people in linked threads confirmed that updated systems do not have such problem.
Moreover, BIOS has important security updates which affect the security of Qubes OS (example), so you definitely should update it. I am not sure that it’s sufficient to have latest microcode in the OS. Their update script is quite safe, no complains on the forum that I’ve seen.