Shallan/Adolin just feels so vanilla/passionless in comparison to Shalladin. Just randomly flipping through the book:
Yeah, she should really ride that wind, right Kal? She really merely reminds you of Tien...
Find me a similar suggestive thought process in Shadolin, I dare you... at this point I am starting to think that all these constant "wind" innuendos are unintentional and Brandon is wholly oblivious to writing them, seeing as what he apparently considers the proper pairing.