[No mocking intended, just a dynamic that Jack's very used to but is probably a little lost on Sam. When he's the one in Sam's place, he craves the reassurance of praise, and so when he's topping, he gives it unreservedly, as well as using it to maintain a connection with someone who can't see him.
He chuckles as he pulls up, massaging Sam's cock with his throat and then his tongue and lips and leaning forward to murmur, low and warm:] You can move now, Sam. Go ahead and let go. Whatever you want to do, I can take it.
[And he dives back down, greedily, onto Sam's cock.]