Yes, it should still provide power through the VBAT pins. See: seeedstudio.com/wiki/images/ … ons-04.jpg
That means that external modules can kill the battery. I’ll check if the core module cuts the battery if any module would drain too much.
I also have turned off the core module (no external modules except the display and audio) and still without a sim, it dropped dead after 2 days. Maybe the main module has too high idle consumption.