Okay, my USB-based Win10 pretends to "sleep", but never actually enters proper suspend state. Perhaps because it is running from USB and suspend might power down the drive?

Or maybe that's what it normally does, which would explain why your notebook isn't in suspend state when unhitched from the dock.

The way I know it didn't really suspend, is the activity LED on the USB drive just keeps blinking away while in "sleep", indicating that Win10 is still doing whatever it is that it does to keep drives continuously busy.

Dunno.