WTP – I don’t have time to rewrite my entire post, but I will try to do part of it.
I have friends with top-daughters from top-seminars who are in shidduchim now, so I know that it is considered completely acceptable and normal for Israeli girls to wait until after the second year of seminary to start dating.
While it is true that they can start during the first year, it is perfectly acceptable to wait until the second year is over or at least until Chanuka or Pesach of the second year. Even those girls who do go out during the first year usually wait until Pesach (or at least Chanuka).
Also, remember that the average Israeli girl is usually older than the average American girl, since parents are more likely to hold back here, and more likely to skip in the US (although that has started to change).
It is rare for girls to get married in 12th grade in EY. It is possible that it happens occasionally, but it happens sometimes in the US as well.
Plus there are many American girls who don’t go to EY for sem, and many of those girls get married during seminary.