The back surgery is concerning, especially given his young age. The fact that he won't submit to medical exams or release his medical records means, in my view, that his back is not fully healed and/or he may need a revision surgery and/or he will need another surgery at some point down the line and/or he will have back problems later in his career. Just say NO to Porter unless he release everything and submits to a medical exam.
edit: I don't see this as him specifically avoiding the Kings because he hasn't release this information to any other teams either.
double edit: drafting Porter under those circumstances should get Vlade fired.