Jack, are you sure both HTSEU and HTSDEE are active for the users? I think when you assign it to the same legal reg ATLAS as in your case, only one can be active which will be HTSDEE.
From your S1 screenshot, I can see both HTSEU and HTSDEE are export related schemes and they should be tied to 102 numbering type, the reason it defaults HTSDEE is for each legal regulation, only one set (export and import) of numbering schemes can be active which in this case happens to be HTSDEE for exports. This control resides in /SAPSLL/TLEGSU.
Hope it helps!
-Shrini