Looks like after chatting with the actual experts, that my battery calibration might be off due to the odd way I normally use my Librem 5 (almost always plugged in either to the wall or to a dock that is doing some level of trickle charge), and rarely have it drop below 90% unless I’m out for an extended amount of time, which is somewhat rare these days. So I don’t really know whether that 10% and lower reading was accurate, or really any of the readings.
I’m going to reset the calibration (power off, remove and re-insert battery, drain to empty where the phone shuts off, then charge to 100%) and then I guess the above Librem 5 battery readings are somewhat questionable so I will probably start by re-doing my most recent test and then go from there.