My whole view is Andrew always viewed football as a job more than a passion. He loved it because he was good not the other way around.
I would guess he got injured again outside of football, but not to the point to prevent him from playing. Like the nagging wrist injury you have that seems to flare up with dull pain every once in a while. And since it wasn't debilitating the medical staff just have him pain meds to deal with it. Since he's dealt with that, and he fell into a dark place from injury before, he promised himself he'd never go that route again. Being newly married, and with a kid on the way he probably questioned if he really wants to put his life outside of football on hold to prevent anythjng from happening.
He's worn down from being injured, probably everyday, for the past 4 years. He wants to enjoy the new life that's on the way soon. And he's going to get beat up again if he keeps playing that will likely require the rehab and treatment he endured before that he clearly doesn't view positively.
The management gave him the time to reset his head, most likely last week. Hoping that when he comes back he falls in love with football again. He went into that practice knowing he didn't love the game and didn't expect it to invigorated his need to play again. Hence thinking it was probably his last time throwing.
I don't blame him. You have enough money for multiple lifetimes, and you aren't in love with your career anymore. I'd probably make the same exact decision. He has more important areas of life than football. It's just a damn game.