Ohhhhhhh, you’re getting onto dodgy territory there missy!
A ruin, especially if you’re doing it for JuNO or similar, is defintely supposed to be you pulling your hand away AS SOON as you go over the point of no return.
Just like that.
Those few strokes after you go over are often the best bit so nope, they aren’t allowed. It’s a sort of ruin, but we don’t want ‘sort of’ do we, we want FULL ON RUINS here, my dear.
So don’t do it again, go forth and ruin properly from henceforth!