> Why is the MOS team so dead set against it?

Fab mentioned "weird issues":

https://morph.zone/modules/newbb_plus/viewtopic.php?forum=11&topic_id=6042&start=38

...and jacadcaps mentioned "funny problems":

https://morph.zone/modules/newbb_plus/viewtopic.php?forum=11&topic_id=6042&start=42

That's all I know. For better information you'd have to ask them.