When using [ShowInInspector] for a private bool field the bool box is visible but not updated to reflect true/false in play mode.
There is a strange issue where using [ShowInInspector] for private bools with some classes derived from abstract classes do occasionally update to reflect the correct value.
Reproducible using simple script attached.
Issue on odin 2.1.12 and 3.0 beta personal.
Editor only mode is off.