The extension has an automatic timeout feature.
You can set it for immediately, or 1 or 5 minutes etc depending on your preferences.
You can also set it to lock or logout, depending on your preferences.
Manual initiation of lock or logout is available with a little more effort as you discovered if you have intermittent needs that are not met through the above automatic timeout features.
I don’t know if this suits your preferences, but to me it seems quite flexible, not at all a fatal flaw imo.