Contrary to Mao's belief, Luke actually wasn't smirking. At least... not with his usual twist of meanness. It was really just more of a smile. Luke didn't actually think to tell Mao how adorable Luke thought he was being (although that probably would've changed the tone of the whole conversation). It might've slipped out if they were actually together, but it was far easier to keep himself in check on the phone.
The smile faded at Mao's next words, however. Really, Luke shouldn't have been at all surprised at Mao's defensiveness, or at his annoyance that Luke was making him initiate everything. This was the game they'd played from the start, after all, but somehow it still managed to get them annoyed at each other. Despite Mao's sulkiness, however, Luke managed to remain surprisingly rational.
"I'm giving you a chance to tell me what you want, Mao. How am I supposed to know if you don't tell me? I'm a Jedi master with the Force shit, but it's not like I can read your mind."