Nah, I think it's for real and it makes sense.
On Rielly's end he's been here for so long and he's tired. A low stress sunny retirement home that wants him as a mentor to the kids as they work towards being competitive is a good move for him. From our end, Chayka knows Mo's analytic profile. He's not what he used to be and he was never good defensively. Might he look better in a new coaches system? Sure, maybe. But he's also 32 yrs old with 4 seasons left at 7.5 million. If you have a chance to move him for value right now, it might be your last chance. If he bounces back he's still flawed Morgan Rielly but now 33 yrs old and if you try to move off of him then, there might not be any takers.
I've loved Mo for a long time, but it makes sense for everyone. Even the best part of his game is replaceable at this point in his career, especially at his AAV.