How often do you get leveled-up Isra/Vidomina from prison? In 1 game out of 20? Out of 50? Out of 100? Well, you got them — good for you, you got lucky.
Especially considering it's hardly an imba in the late game — there are more important things to do than gathering skeletons. Especially on Jebus Cross, where the majority of controversial episodes will occur.
In my opinion, a properly placed external dwelling of angels or a mini-Griffin Conservatory is a much bigger imba in terms of impact on game outcome.
The number of rules and bans should be minimized as much as possible. You won't achieve balance of layouts with them anyway, so only the most egregious things that drastically affect gameplay should be restricted. And all kinds of minor luck are easier to allow than to ban and then monitor.