I can invert or remove the mask (or anything) using the space outside of the white line in ZBrush 2021.
As far as the video, it looks like you are correct so I apologize for my mistake. I can’t confirm it on my end as I don’t have 2019 installed. In any case, issues like that should be directed towards the developers via a Support Conversation. Nobody on the forum will be able to fix it for you.