As I understand it:

Even though you are being held back, you are for all intents and purposes here at DAL for bidding, longevity, etc. You have an aircraft assignment, and can bid on the AE here in a few weeks. If awarded something different than what you are assigned, that means if is a new award, and the seat lock applies. That is how I read your status here at DAL.
Because of this status, the contract will effect you like you are sitting in class with the others that started that day.

Of note, even if awarded another jet, that does not mean you will not go train on your initial assignment. This AE will more than likely have a conversion window a few months past the day you show up. If they cannot contractually get you in to training on the awarded jet from the next AE, you will be doing two training events back to back. Trust me it can happen. Just realize that.