Opacity slider in Eraser tool?

I am very confused about the Opacity slider in the Eraser tool. When I set it to, say 15%, I thought it would only erase up to 15% of the mask, no matter how many times I brush over the same area. That is what Photoshop does. But in my Capture One 22, if I release the mouse, or the stylus, and brush over the same area again, it keeps building up the effect. I thought that's what Flow is supposed to do, and Opacity is supposed to limit the total amount of the effect. Again, this is what Photoshop does, and it makes perfect sense.

Why does Capture One do it differently? Or is there another setting that can limit the amount of the effect, no matter how many brush strokes are used?