Short answer as xeizo said
😉 .
Long answer
🙂 , the CPU will not idle in UEFI the same as it does in OS. If you had a wall plug meter, you'd see complete system could be pulling ~120W, where as idle in OS is ~60W.
UEFI is a mini OS, CPU boosts in UEFI, so you see voltages for that context. In my opinion Ryzen FW/UEFI is not optimised for that case, so just ignore, use the UEFI to set settings, not for sitting in and watching
😄 ...