Bug with Subject\Background masks

If you create such a mask and then use a brush to draw something on top of it, it will still remain dynamic. If you synchronize it, it will be calculated anew in the next photo, but without using a brush. But if you press Ctrl+Z after drawing with a brush, the mask will become rasterized, continuing to press Ctrl+Z in the hope of returning to the state of the mask before applying the brush, you cancel the creation of the mask. That is, if you draw something with a brush on top of the created mask, you cannot undo this action without losing the dynamic mask.