It gets worse, pressing ANY key during the voicemail greeting will transfer to the operator extension. It's a huge nuisance in places with separate departments or business entities, or call centers with several different queues / projects that shouldn't mix together.
As far as I know, it can't be disabled.
Once a user records their greeting that prompt won't play, so that's good. However lots of people dial 0 and expect to be transferred back somewhere even without giving them the option. Would be nice to chose where that goes for each extension or extension group.
You can change the operator extension in settings / PBX settings - first option. You can send it back to your main digital receptionist, a special ring group, whatever works for your situation.