Please could this get to an ESRI consultant as a request.
Having groups in the TOC of ArcGIS Pro is useful, like it is in ArcGIS, however the order of the items within the group should be independent with respect to the layout i.e. if I group like items together, like rectangular frames, I should be able to independently determine whether they appear above or below other items in the layout, which may appear above them in the TOC.
Thanks,
Nigel