True. Inkscape, unfortunately, doesn't really understand dimensions. Internally, it uses "px" as a unit, although SVG understands "mm" and "in". Corel Draw is more serious about dimensions and units, which is needed when you're talking to a laser cutter. SVG users have asked for the opposite feature: roundoff to pixel boundaries, instead of floating point coordinates.[1] SVG's internal representation is a text string of a number with a decimal point, but it's up to the program writing the file to decide how many digits to put after the decimal point. And, of course, you'll get rounding errors going back and forth from text representation to internal floating point representation.
[1] https://bugs.launchpad.net/inkscape/+bug/951655