[Q] Snap existing vertices/nodes to a layout grid

I ploughed through existing posts but I’m still confused about this:

I have a layout grid on a frame. When I draw a new rectangle it snaps perfectly to the grid. After drawing the rect when I move the sides they still snap.

But when I turn the rect into a closed vectorline through a double click, the corner vertices refuse to snap to the grid.

Is that normal behaviour?