As mentioned above: this whole process comes across as a dubious business practice. A new low with respect to the traveler's airline experience. Here's the synopsis:

Delta makes significant changes to my reservation without my asking/request to do so.
I look for options that suits my needs via Delta's flight modification process through logging into Sky Miles.
I can't rebook a flight that shows as available by checking the flight availability as if I am making a new reservation from scratch. The rebooking attempt through Sky Miles shows as "unavailable" or "not offered". These words are the exact verbage.
If I request a flight e-credit and try to rebook using the credit it won't cover the cost of a new reservation (same travel day, same seat class). Gee, how economically "convenient" for Delta, huh?

For those who fall victim to these shenanigans there is a process for fighting back.

https://airconsumer.dot.gov/escompla...nsumerForm.cfm

I have already started my official Consumer Right's complaint form.