Maybe for LAS, but not for Florida. I have just checked random Song flights from LGA to FLL in October and none show rows 16 or 17 available. Possibly this is because it is just too stupid to force Medallions to change when a nonstop transcon is available, but they consider ATL a convenient waystation on the way to Florida.
It seems to me to be idiotic for any company to deliberately inconvenience some of its best customers, but DL does it every day to its Medallion flyers who prefer a nonstop to Florida.

I close my comments on this thread for tonight with this story from the deep reaches of my memory:

Many years ago, my regular carrier to Florida from NY was Northeast Airlines, but I did not follow what was going on in the airline industry very closely. Some of the veterans here may remember the "Yellowbirds," which derived that nickname from the garish shade of yellow in which the planes were painted.
One evening, as I was planning to buy a ticket to Fla, I as usual dialed up Northeast and was surprised to hear the voice on the other end say "Delta Airlines." I asked who was Delta and she told me that Delta had bought out Northeast and was now providing the service that I was seeking. Sounded OK to me and I gave her my dates and times and she came back very quickly with an itinerary at about the same price that I had been paying Northeast. However, there was one catch. The trips were more than 5 hours long and I was accustomed to NY-Florida in about 3 or so. So I asked and got the answer that I would need to change in Atlanta. Flabbergasted, I said to her something like "Change at Atlanta? That's nuts. Nobody is going to do that and you'll never make it in this market. I think that you'd better get the money back from Northeast."
Shows how much I knew about where air travel was going. But I do know where I'm going now. Just as I went over to Eastern Airlines all those years ago and gave Delta very little of my business over those years, I will now go away from Song and DLs service over Atlanta.