I am using MPy and have similar behavior to Terry.

Using the initsetup.py logo as a test app as a baseline:
Without battery) It takes ~3 seconds for the LCD to light up and show the logo. I can reliably repeat the unplug/plug-in process and ~3 seconds is a very good estimate...

With battery) there is no indication the device is powered... I plug in the USB, hit the RST button and the log comes up after 3 seconds. Now when I unplug/ plugin the USB port the LCD is on / off instantly.

The behaviors suggest that the battery alone won't boot the system, nor will it keep the LCD lit but the board itself remains powered.

Definitely need clarity here as to what we should be expecting. Eliminating the need for an external boost power supply is a core feature I am interested.

Also wondering if it's safe to power the board via the 5v port...