Hi! I'm having similar problems, I export .SVG files to be processed and rasterized with Python and the sizes are sometimes all over the place.
So far, the only solution I have is to ensure that I export things with the following options (here from the :
Area : *Whole document*
Rasterize: *Unsupported properties*
Flatten transform : *On*
Set view box : *On*
and everything else OFF. I also resize the image to the precise size I want the rasterized images to be... I hope this helps!
I attach a screenshot with the same options, this time from Affinity Design desktop (OSX), which I downloaded just to see if I could overcome that issue