So I took my question to WGT and after a bit of prodding, I received the following answer:
"If a player disconnected, that round would end as this game mode
requires 4 players to complete. Please note that as this game mode doesn't
count towards a players stats or average, similar to a practice round, if this
happens it would not negatively affect your progress in game."
Soooo, they are saying this happens because one of the players (probably on the losing team) just decided to walk away.
But I agree with your comment that in these cases, it appears the pair in the lead are credited with a win in their Stats.