How does the league define assists? I don't know. I just know watching the game is not one of the method they use to determine who gets an assist.
It surprised me that Frankie didnt get the secondary assist since MLS usually gives them away pretty easily. My take on how they give assists away was pretty much if the ball touched you, whether you meant to touch it or not, and the next person (or two people later) put it in. I've seen much lamer assists given and really thought Frankie deserved one. (Plus he's on my MFLS team )