I was always under the impression that the plays in a parlay would have to be decided when the wager was submitted. Recently i tried to make a single straight play while i was in the parlay screen.... it forced me to enter it as a two teamer: one pending play, one open slot.
in that case.. isnt it in someones interest to make every play an open 2 or 3 teamer parlay?
then you can lock in the line you want and always have a later option of keeping it as a straight play, or adding additional selections to make a parlay?
If you make it an open parlay you don't have the option of keeping it a straight play. You eventually have to fill the open slot. I normally use big favs that come up later that I wouldn't bet straight.