In addition, a vpgrid takes all properties a viewport can, and the following groups of style properties:
Common Properties Position Style Properties
Position Style Properties
xmaximum - int
ymaximum - int
maximum - tuple of (int, int)
xminimum - int
yminimum - int
minimum - tuple of (int, int)
xsize - int
ysize - int
xysize - tuple of (int, int)
So, this was a change in 7.3.3, albeit a obscure one - the xminimum and yminimum properties weren't listed as position properties. If a vpgrid has a side, position properties go to the side containing it, and not the viewport itself. To give the xminimum to the viewport, you need to use viewport_xminimum: