The rule is this:
There is NO rule that says you have to be any age to play in the AHL. The rule is that a junior aged player cannot be sent down to the minor leagues without being first optioned back to his junior club. Every year multiple players get sent down to the AHL after their junior teams are eliminated from the playoffs and are done their seasons. This same thing came up last year with Dan Blackburn. Danny Fritsche got sent down a week ago, and no one even noticed. But since MAFs team is done with their season he can be sent to the AHL, the same woulod have applied if he was sent down from the NHL and would have never gone back to juniors. Technically he could have been sent down from the start of the season as long as they optioned him back to Cape Breton and they said it was OK and that they didnt want him.