OK, that’s interesting. My theory would be that the charger momentarily stops to supply power because of USB-C PD renegotiation.
BTW everyone in this thread: we’ve released the first version of reform-power-daemon via an update for reform-tools, version 1.82 which is now in Debian (thanks @josch!).
To see if it does the right thing, run this command and unplug / replug the charger:
sudo journalctl -u reform-power-daemon -f
It should change the CPU and GPU governors depending on charging or discharing state. Also, it might be necessary to uninstall tuned* and power-profiles-daemon is present until we have a clean integration with these daemons.
(And yes, there’s a silly but harmless mistake in the beginning of the script where it checks the FW version numbers, will be fixed ASAP).