xfc4 ends session (logs out) on critical power level

I'm on current Ubuntu LTS 20.04 (not Xubuntu). Power manager settings for "Critical power" are:

Critical battery power leve: 10% 
On critical power: Ask

However, when power reaches the critical level, the session is ended (I'm logged out) and I see the log-in screen. The laptop does not suspend.

This is on a Thinkpad X260 (in case it matters).