As a soon to be new joiner (DEFO) I'd like to add my two cents worth...
I did not apply to CX as an SO for this exact reason! All those that did apply as such accepted the job knowing that this was the reality. I agree that it is wrong that they are treated as such so I do empathize with them. However, I do not sympathize with them because they knew the deal and chose to take it. How many of those SO's chose the job because they could not meet the minimums for DEFO? Half? At least a quarter of them. Now because they have three years with the company, they think they should be able to alter the agreement they signed. I just do not agree with that. Again, I do agree that CX should't run the SO/FO progression as they do; it is not my job to determine how CX should run the company. If it was my job, I would start everyone off as SO and they would work their way up to command.