Hi @Bleke,
I think exact this has been a topic two or three times in the past weeks, if I understand your question correctly, and the devs probably know about it by now.
Since this behavior doesn’t bother me myself, I even want this to have a larger painting area, but I only roughly skimmed these topics and didn’t care much about it, but I believe there is either a bug report or a wish bug report about it. You could try to find this topic with the forum search engine, and I will also try to find it again and let you know if I succeed.
Michelist
Edit: There it is: