Well, here I am answering my own question... After continuing to dig I found
an obscure reference to IVsPropertyPage that does the trick. It's a bit of
an odd puppy as it contains only one method that the IDE calls repeatedly to
get the "path" for the property page in the tree view.  The docs make a note
that the IDE currently only supports two levels of sub categories so I added
the following code to my property page as a test and sure enough I got a
tree view that had 'cat2\cat2\mypropertypage' (NOTE: no cat3 and TWO cat2
entries) no cat3 is actually expected as the docs say the IDE only supports
2 levels at this time but the duplicate cat2 entries is unexpected and I
can't figure out how to get past that as this API is anything but
intuitively obvious to the casual observer. :(

int IVsPropertyPage.CategoryTitle(uint iLevel, out string Category)
{
   switch(iLevel)
   {
   case 0:
       Category = "cat1";
       return VSConstants.S_OK;
   case 1:
       Category = "cat2";
       return VSConstants.S_OK;
   case 3:
       Category = "cat3";
       return VSConstants.S_OK;
   default:
       Category = null;
       return VSConstants.S_FALSE;
   }
}