Joey was signed to the Rangers as a forward. He knew this going in. He was put back on D only because he had played D at one time and the situation was dire. He very well may have felt that he wanted to stay on D but the team signed him to be a forward. Feelings aside, that's not what he was contracted for. So somewhere between saying "yes, I want to stay on to my OA year" to now, he has decided that playing forward is not what he wants and playing pro D (maybe Europe) is. Good on him.
Beginning with the 2018 playoffs, he was much more valuable to this team as a defenseman. It's a position he wanted to play. Just because he was drafted as a forward doesn't mean it had to be written in stone that he can only be a forward as a Ranger. Andre Benoit was drafted as a forward too. We all know how his career in Kitchener and the pros played out.
The bottom line is the team did not want him to play defence full-time. The team knew full well long before the period of time leading up to the trade deadline that he wanted to play defence full-time. It wasn't a secret.
As far as I'm concerned, this is a disgruntled player. He was not happy playing forward and knew he would not get the chance to play D based on where they played him last year - especially post trade deadline. The final nail in the coffin was how our import draft went.
We don't know how he was asked about his OA season before the deadline. Was he led to believe that if he plays an overage season he would or could be utilized as a defenseman? Or, did they tell him that his future in Kitchener was only as a forward? How this conversation went we likely will never know.
One thing we must assume is that at the time he agreed that he would play an overage season here, he either had a good idea from management that there was a possibility that he would be utilized on D or that he was told he would not be and maybe decided to let the team think he would play an overage season here anyway to avoid being traded at the deadline. If MM is doing his job, and he knows Garreffa is not coming back for an overage season, he should be trying to move him at the last deadline to get what he can for him since last year was not a contending season. We likely would have seen him dealt instead of McHugh. MM likely felt that Garreffa was more valuable to the Rangers then McHugh as a forward this season.
MM probably figured that Joey would come back for his overage season, and even though he would want and expect to play defense, could get away with one more year of bouncing him back-and-forth between F and D.