Nechomah, as I am not familiar with exact procedures mentioned here, I do not have an opinion on how rigorous they are and – if they have lower standards – whether they are justified. I just pointed out one extra consideration for these conversions v. , say, someone converting in NYC for marriage considerations.
BY1212, we were able to take at least a million of Jewish souls in the 90s who were behind the iron curtain for 70 years already. I don’t think there was an ability to immediately vet all families for everyone being Jewish, and presumably there would be many who would stay if their non-Jewish spouses were not allowed in. There was no way to predict whether USSR was dissolved forever or would come back in 5 years or would be a mild dictatorship like it is now. US and Israel succeeded before with getting a trickle of Soviet Jews out in the 70s and then it stopped.
Halachically, when we do pidyon sheviim – do we vet every person to be a Jew, or can we just say, there is 50% surcharge for saving each of the Jews?
Also, note that these non-Jews married Jews in an anti-Semitic country. How bad can they be (I am sure some are, I am talking averages here).