There is
-
Device specific mitigation configuration for dealing with overheating, low battery, etc defined by device manufacturer / chipset vendor / like entity with knowledge about low level hw details
-
Generic SailfishOs power saving mode
These are independent of each other and activating/deactivating power saving mode does not have any effect on performance tuning items like clock rates etc.
Basically a notification is shown whenever there is a change in “power save mode is active” state i.e. value of expression
psmActive = (batteryLevel < threshold AND charger == disconnected)
changes. And in this case attaching a charger causes such change.