An issue affecting all of this is that westbound (by day) TATL in D1 just isn't as valuable as eastbound (overnight) D1, certainly to the eastern US. KLM wants to monetize empty westbound sleeper seats as a cheap upgrade; DL sees them as a painless way to satisfy elites using GUCs.

I found westbound on Norwegian in a Business seat to be more comfortable than being awake in a D1 seat. $699 last summer MAD-JFK.