The player, in conjunction with the team, chooses the rehab program. It’s a collaborative relationship and decision. Neither side “dictates” anything to the other.
The GM and training staff could have gotten together with Perron and his agent, and they could have discussed the best course of action. It could have been decided that considering Perron’s age and the nature of back injuries, it’s best to be extra cautious and give him as much time as possible to recover. Perhaps take things slow with the goal of getting him back on the ice in March so he could be ready for a playoff run. Perron could have said, you know what, that makes sense. I want to be 100% for the playoffs and next season. Maybe play beyond that. I don’t want to risk worsening it by coming back too soon. That, of course, would have given the team the benefit of LTIR cap space. But that wouldn’t have been why that course of recovery was taken. No no, absolutely not!
That’s how things work. It’s not magic.
Of course, to my original point, the team and Perron clearly chose not to do that.
But your original question was how could they clear 3.75M? That’s how.
And it could still happen.