The contents are rendered through gtk/cairo which not only goes through https://www.xquartz.org/ but also doesn't use GPU rendering (it was experimental 3 years ago, maybe better now). The main issue seems to be that neither Inkscape nor gtk people have low level Darwin experts or time available to invest in debugging the whole rendering stack. See for example https://gitlab.com/inkscape/inkscape/-/issues/1614 and all the other referenced issues for all the gory details.