I think that the other responses indicate that because FlyI is an 100%-e-ticket based airline that will be liquidating, we do not know the exact manner with which the other airlines honor your independence air reservations. Nothing has been mentioned as to how Indy passengers are supposed to deal with this issue in requesting a seat on another airline on a standby basis.
IMHO, calling the method above as "the deal of lifetime" isn't exactly ethical. We all know it's meant to SAVE Indy passengers who otherwise would possibly not be able to afford the high walkup fares. To use this to a solely personal travel desires beyond necessary extend would be incorrect.