BluesBrothers: The Soviets banned them and they grew faster underground. I grew up on stories of the brave JW's behind the Iron Curtain and those who smuggled in the literature. They were an inspiration to us all , and proof ( to us) that Satan could not thwart Jehovah's Organisation.
Well...that is what you were told. I don't think they grew faster - that sounds like a WT myth. I am not convinced.
There are several accounts of those banned, isolated little bands of JWs who emerged from hiding with copies of Rutherford literature clutched tightly in their hands. Which they rigorously defended, never re-joining the new and improved WTS. They view the WTS as "apostate" because the doctrine changed so much during their dark ages.
There is one of those groups that uploaded material to archive.org a few years ago. They call themselves the "Theocracy Publishers":
https://archive.org/search.php?query=theocracy%20publishers
I am wondering if those isolated little groups of JWs, are the ones that are a point of contention mentioned in the court when "unregistered" congregations are being discussed as to whether the ban should include them or not (sorry...can't find that part right now). It seems like there is some confusion as to if the Admin Center oversees all of them (?).