The only complaint you may have is why the other team is deciding to make up the games. If you don't have a legal line-up by some predetermined time, you forfeit the game unless an emergency situation arises. Just because you don't have a legal line-up doesn't mean you automatically qualify for a post-bowl situation. Most often though, no one will argue this point because you would want the same opportunity provided to you in the same situation.
Just to make it clear, here is an example:
League starts practice at 6:20 and competition starts at 6:30. When 6:30 comes around, Team A needs 3 of 5 members present to make a legal line-up but only has 2. Team A must have a legal line-up before the end of the 4th frame or will have to forfeit the game. The members of Team A present say the other members are either going to not make it that night or are simply "running late" and will be there shortly. Team B can either bowl slow, wait for the other members or just bowl as usual and if the members make it in time, fine. However, the Team A members that are present say they will post bowl so they don't have to forfeit. They may realize enough members to make a legal line-up will not be there in time to bowl the first game. After they say they will post bowl, they may call everyone who may have been enroute and pass the word. I am not saying this is wrong, but I have been bitten by the post bowl/emergency situation rule before. Most league rules state that post/pre bowls are for emergencies only.
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I am not a pro-bowler, but I do play one on BallReviews.com