This seems like an oversight - unless I’m missing something, when selecting “Use current CPlane” the Position coordinates should update like the Size ones do.
Over the past year or so the BoxEdit panel has become a workflow staple for certain drafting stages here - it’s a great UI feature, I find having these coordinates fields immediately editable in an open dialog is one of the quickest ways to rapidly check, enter and rationalize point positions. Would be very helpful if it worked consistently in conjunction with CPlanes.
eta - ah, looks like it does get updated when “Use Bounding Boxes” is active. So perhaps only Use Gumball" is affected