In which case I do think it'd be cheaper for Criterion to have everything including on the UHD disc rather than turning a UHD-only release into a DF just for this. Several labels are choosing UHD-only releases instead of going their route (which is rather the US studios route). The only financial nuance I might see is when it requires to use a UHD-100 instead of a UHD-66 (though actually, with so many crap encodes already, they might just be able to compress even more the movie and the encode will still be crap anyway so would there be a visible difference ?), but they have several cases of UHD-100 with space left anyway (Time Bandits has 13.5 Gb left, Dreams has 11, Don't Look Now 13.5, etc). And they have cases like Branded to Kill, which has 5-6 Gb left and not much extra features.
I found those : Heaven's Gate, Seven Samurai, Brazil, A Brighter Summer Day, Short Cuts, Barry Lyndon and The Irishman.