NoteGroups::createScore() - why custom page margins for this new score?

When is this function called? Why does it set its own version of default page margins here:
https://github.com/musescore/MuseScore/blob/33a1dae28ed55faddde5952936a…

From what I can tell searching the forums (it's not in the handbook, afaict), this is a way to group sub-divisions within a measure, so that you can distinguish 7/8 as 4+3/8 versus 3+4/8. But I've never used this feature.

Mainly I'm wondering about the margins. Why set special margins for this new score created this way?