For vector backends, it should be acceptable for the output canvas to have a noninteger size. Indeed, the pdf backend will output canvas with noninteger sizes "as is". On the other hand, the svg backend truncates the output to the integer below, which it doesn't need to do.
Activity
tacaswell commented on Nov 19, 2017
It appears have been this way since at least 2005 but see no reason for it to be so.
API: do not truncate the total size of svg element to integers