MRJ has never said no to them. When they needed Neal, they got him.
This is different,MRJ went one time,if he had been in more epis than 512, i could agree that he really loves everyone and would return everytime they ask him, but like he said after, he did 512 to give the character a end, a closure for fans to know Neal was happy( even tho he was dead), he could totally refuse now, bc he was not going there to do what could have been and then still be death and unlike Sean not even appear in other epis. Even Sean said in interviews, he said if was to do flashback he would not go, he was going to do in order to give OQ fans closure and have a actual story, that appears will be in 5 epis
"I offended you with my opinion? Ha, you should hear the ones I keep to myself".