Thanks for the GA education FoF. I can see how they might place emphasis in some states on the CP's religious status if there's a bent towards giving the CP more control, and that would carry weight as well as precedent. In TX when they implemented joint legal they truly took the CP status down to "residential" status, where they can pick the residence for schooling purposes, and also receive CS. There's a lot of teeth in the joint legal here to give both CP's & NCP's input into major decisions, so I think I errored on making my reasoning too broad.
I did notice in reading through the dozens of cited cases that it' seems that those of the jewish faith are the ones to get so bent out of shape about it that they take it all the way through the courts. Why that is, we'll just have to guess.
From my Jewish friends I am aware that in a couple of Jewish denominations that there is a maternal inheritance of your association with the faith. You cannot "convert" per-se later, or there are huge complexities around it. I also know of significant worry about diluting the faith due to inter-marriage, due to either conversion or non practicing of the faith by the one who intermarries. So I suspect those are drivers.
This was an enlightening exchange.