Yeah, but is exploiting a loophole really illegal? (Notice I didn't ask if it was unethical.)
The law says divorced. It doesn't say divorced and stay that way. I've heard of other cases where people have gotten divorced because of things like medical or disability benefits only working if they are not married, etc. There was no outcry over those and in some cases it was actually suggested by the benefit provider or legal system.
The way airline management is today, I don't know if I really blame these guys for doing what they did. It's being talked about on an airline forum and the consensus there is that as long as no laws were broken, more power to them for finding the loophole. The feeling is that the airline will try and find a way to cancel the benefits so why not protect them within what the law allows.