Yup.  That was the case. TomAYto, TomAHto, it does make a difference in this case. Those little check boxes to Allow Degrading that you HAVE to have ticked in order for the FBX exported to proceed are having an affect on the interim obj format that it uses. Usually not an issue.But, since I don't have morphs exporting anyway, there's no reason to use that geometry, just the rigging, and use an OBJ directly from DS. I can transfer the weight mapping later to the OBJ.

I still have a lot of poking at this to do, but if I leave most alone, & DON'T MERGE points but DO SCALE the morph object to 1% so both objects match, then select the polys by surface, and do various copy & pasting, & put my tongue out the left corner of my mouth, but no more that 3/16", the morph transfer works and almost instantly. You probably don't have to do that last step, but it worked for me when doing that, so who knows. It's all Black Magic with numbers anyway.

Obviously, doing this in DS would be preferably (would then export as FBX), but at least there appears to be a means.

Here are some partials of what I mean: