Almost certainly it had been emphasized to president Trump (and probably known to him for decades) that Arabs find it offensive to drink or eat with the left hand (out of concerns for hygiene), so when he started sipping his tea with his left hand, and looking around to see who was watching (then quickly correcting of course), you gotta believe it was his mischievous side coming out, perhaps sweet revenge for having to do the Sword Dance with some who may have been Wahhabis.
