These are not apples to apples comparisons.
Gronk had documented frustrations with the team he was on, while Edelman has had nothing but good things to say about Belichick and the Patriots.
Gronk didn't film a goodbye video, on the field at Gillette, with the words Foxboro Forever. Not retiring after doing that would look very disingenuous and not be in line with Edelman's personality.
Gronk was 29 when he retired, meaning he was still only 30 after a year off to heal. Edelman is 34 and has no cartilage in his knee.
Yeah, comparing this to Gronk is a bit disrespectful to Jules. People are making it sound like Edelman (or Gronk for that matter) is using a retirement to shoot his way out of town to play for Brady and that clearly isn't the case.
It seems pretty clear that Edelman's knee is dictating this retirement, not Edelman himself. From the sounds of it, Edelman would play tomorrow if he could physically.
Gronk was just tired of the punishment his body and his situation and needed to get away. If he wanted to play, he could have. It clearly wasn't physical because the first thing he did upon retirement was run to the WWE to try to become a wrestler. Even when he retired, people talked about that it could be a one year deal and he would be back in 2020.