One good thing I saw in the T&Cs was explicit clarification about SDC:
If you have a Delta Comfort, Delta First, Delta Premium Select or Delta One ticket, you may make a Same-Day Confirmed change as long as a seat is available in the cabin purchased or you may change to a lower cabin if available.
This is in contrast with main cabin stating is needs to be in the same fare class. Except, DL is hiding the fare class so you don't know what it is when getting flight results. Insane