Figured I'd report how it worked for us.
We decided to give it a try on Sunday (12/20)
About 6:00 we walked up and asked about the wait (for 4)
They told us about 15-20 min so we gave them our number to text (by the way, most places are using the text feature now, even with an ADR. they text you when it's time to be seated, instead of giving you a beeper)
They told us to remain near by (so I don't think they suggest you head off to Tomorrow Land)
DH and DGD went to ride Magic Carpets
DD and I sat in the entry area.
5 min later they called our name to be seated. Thank goodness we stayed in the area
DD went to get DH and DGD, I went to sit down, they came in a few minutes later
20 min later I got a text from DH that he had gotten a text to be seated. This is going to be where issue arise. WiFi and Cell signal was very sluggish during our trip. I kept WiFi off most of the time, it was so bad. But our texts were often 10-15 min delayed in sending. I'm not sure how they'll handle it when there are delays in sending your text and you receiving your text