I have “Fit to window” enabled and it’s not using about 36 (18 below, 18 above) pixels of available space. I’d love to get these extra pixels back, as I simply cannot work without them.
Padding is a deliberate design choice and not a bug. If you would like it changed, then you should file a feature request. See:
for what constitutes a feature/bug and how to adequately report/request them.