No, you don't come home to a surprise, but if you are marrying a woman from the FSU, in most cases, you've spent a few weeks here and there with her, and then 90 days on a fiancee visa. You may be in love, your children have no say in the matter.
I lived in Ukraine for a lengthy period, I am from the Ukrainian diaspora, speak Ukrainian fluently (used to speak fluent Russian, but I haven't bothered keeping it up, but it's still better than that of 99% of foreigners), and I know a lot of FSU Russians and Ukrainians here. Those communities tend to "stick" together, particularly through churches and cultural events. So, I've seen a lot of marriages. While I obviously am not a party to the marriage, nothing surprises me.
The man I knew in Ukraine - first wife cheated on him, so he divorced her. He was 19 when he married her, so that tells me that she was pregnant, and that, rather than some great love, was the impetus for the marriage. This was extremely common in the USSR (i.e., young girl getting pregnant, and an early marriage). Second wife died, so you can't really blame him on that one. Third wife was a rebound to the death, cheated on him as well, so he divorced her. The fact that he, as a man, had custody of all his children, suggests that his first and third wives dumped those children, because in the USSR, women almost never lost custody of their children, even if they were alcoholics. So, I can't really say his marriages were all failures, only the third one, really. His fourth wife was a gem, a really beautiful soul, and he stayed with her until his death, over 25 years.
American mothers may get custody, but in most states, joint custody is the default, and most men stay in their children's lives. That is not the case in the FSU, at least not the Slavic parts. You just can't say the situations are analogous, because they are not, in any way.
I disagree that being family oriented toward your family and not toward non biological children is counter intuitive. Plus, I'm not the one saying they're loving and nurturing. Some are, some aren't. Just as everywhere else in the world. The mistake WM make is to believe that FSUW are superior to WW in their "family values". Again, some are, some aren't.