PC in and out standby mode when mobile is connected

When I connect my mobile via USB to my Win11 PC, it goes to standby after 10min of inactivity as normal. However, after 10s the PC automatically starts itself up again. This is just pure nonsense. How can it be stopped? PS: It doesn't seem to matter wheter selective USB energy saving is disabled or not.

Question by Cyman on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.