The US style of having trials for everything seems so odd when you come for a country which simply has sent the three fastest athletes that beat the minimum qualifying standard. It puts so much additional strain on runners having to squeeze in an extra marathon. It seems entirely useless. Rank them after time and send the best ones.
Except that if you do it that way, then you end up with runners trying to squeeze in extra marathons when they think they're one of the top 3, only to get bumped out when someone else runs faster.