A long time ago, I was interacting with the moderator of the list that I still "hang out with" (virtually speaking) and we were on the subject of Protestant to RCC conversions. We were talking about the conversion of Cardinal John. H. Newman at that time.
The moderator happened to be a history buff. He said that in the 1800s it was not uncommon for people to think that prominent Protestants who convert to RCC must have been a Vatican in-plant. Newman must have been suspected as one of them. He said the whole design was to make a massive public impression to sway the Protestant world to kiss the Pope's ring and return 'home'.
In terrorism parlance, I think this is akin to 'sleeper cells'.
I imagine it works like this; first they inject the agent into the denomination (for example - Lutheranism). The agent then works hard to rise in prominence as staunch defender of their tradition (for example defender of Confessional Lutheran orthodoxy), i.e. the guy is known to be Mr. Gnesio_Lutheran himself(in case of Baptist, a Spurgeon resurrected, in case of Presbyterian a B. B. Warfield from the dead). Then at the height of glory/ popularity, convert to Rome. All the rest sees this and disillusionment happens. Impressive and brilliant strategy, won't you say?
This boils down to crypto-something. I do not think there are remaining crypto-Calvinists in Concordia Land. The reason is there is no reason to be there. They are no longer persecuted and no need to appear Lutheran when in fact Calvinist. They just leave with no hoopla. But what about crypto-Popers? You bet they are there. 100%. They often hide under the label - Confessional. Why of course, why would they not covet the label that opens doctrinal doors, why covet the label Liberal, who would take notice? Who would care, if the guy ain't orthodox anyway, what is to lose? But no, boy the word 'confessional', that gets the attention. Fr. Neuhaus that well known Lutheran church man identified himself as 'confessional' and now he is a loyal priest of Rome. I think one day 'confessional Lutheran' will mean -- 'I am on my way to the Vatican or Constantinople'. Sometimes I think I should drop that adjective. I have been called far worst names before, some of them not exactly true anyway, why would I care what people call me, I am a nerd.
It seems when these 'in-plants' are awakened (activated) and they go, you will find evidence that they were never convinced of JBFA in the first place. I will bet that very likely they were, if not now, crypto-Universalists too. See for example Neuhaus' wikepedia article of how he expresses hope in universal salvation.
In Concordia Land, I notice, crypto-Poping and crypto-Universalism go hand in hand. Seems to me, you start doing crypto-Poping when JBFA is no longer your thing.