Join in progress feature in DF.

[Razzle]

And how many would pick the "start a new party" instead of the "Join party in progress only" option if it exsisted? (hint: no one lol)
And how many parties would be in progress if there is no one to start them? (hint: 0)

In other words, it doesn't make sense to have "Join only parties in progress". Because then no one would be STARTING parties...

The tick is there to verify the player agrees to also join parties in progress, not to make sure he joins party in progress only.