Yes, it seems a window in a polywall can't be stretched on plan using the hotspots.
Even a window without a reveal behaves the same way. It stays the same width as when it was first placed and only the hotspots move.
Thankfully you still can type the width manually in the windows settings dialog box, and also stretch it in the 3d window, so at least there are workarounds until it gets fixed. Another thing to try is using the eyedropper on a rogue window, then any new ones placed afterwards will be of the right size.
It's still a bug though!