Thanks for the replies.
To the sanctimonious types, spare me. I spend $60k a year with Southwest and fly 2-3x a week. Sometimes in order to avoid a 5x increase in fare price or to make sure I can get where I need to be should plans change, I book multiple routes which Southwest always ends up getting the revenue on at the end of the day.
For those who contributed info, I think what clearly triggered it was that I had 2 flights at approximately the same time, which is not the case when I've done this in the past. If that's the only thing that gets flagged, I understand the logic. What I don't understand is why cancel it 16 days out as opposed to shortly after I booked it (30 days out) or perhaps closer to the actual flight? 16 days seems like a random guess. I've done this on more expensive flights which I'd assume are more full and have never had a problem, even 24 hours out but clearly they weren't at the same times so that was the key variable.