I am sure that there are others more qualified to get into a discussion about this however my understanding was more in line with how it is described below:
"Despite this, Iwama Ryu was never officially declared an organisation independent of the Aikikai, and it can be regarded as a rather informal network held together by the fact that Saito sensei gave out his own dan ranks - Iwama Ryu ranks - as well as dan ranks from the Aikikai Hombu. Specific weapons ranks and weapon transmission scrolls were also given within the Iwama Ryu" (Wikipedia)
Maybe there were some dojo's that broke away from the Aikikai to later to rejoin, although I have never heard of it, at least not in my neck of the woods.
When Iwama Ryu was active, the national aikido-federation in Sweden had three subgroups based on "style": Aikikai, Ki-Aikido and Iwama Ryu.
OTOH, as far as I know, no dojo in Sweden is affiliated directly with Aikikai (the national aikido-federation is however a member of IAF), so swedish aikidoka becomes an Aikikai member when he/she becomes shodan (with the Aikikai). According to the swedish translation regarding regulation regarding Aikikai dan ranks, ranks can not be taken back. And since Iwama Ryu-ranks were a rather late invention all the senior practitioners had Aikikai-ranks as well.
So you can say that the senior practitioners had a "full-hedge" regarding the future while the junior ones only had Iwama Ryu-ranks and were dependent on that organisation.Luckily, when "Iwama Ryu" rejoined Aikikai in Sweden all of the junior dan ranks were converted to Aikikai.