Looking at the definition of poach, as it relates to this context, the subtext seems to be of the case where an employee leaves without warning or discussion of why they no longer want to remain at their place of employment. Like you cannot save an elephant after it has been poached, but maybe you could have if you know that there was a problem. The poach is the realization that you didn't see it coming.

Of course, the employee is free to just up and walk away at any time, but if you feel it is courtesy to discuss the relationship before parting, and it wasn't discussed, then poach does not seem completely inappropriate.

Having said that, in this case, we don't know many details about the parting. He and Apple may have had a good discussion about the future and came to a realization that the relationship wasn't going to work anymore, for whatever reason, and parted amicably.

From another perspective, perhaps we should not even think of employer/employee agreements to be relationships in this day in age?