It has absolutely nothing to do with immutability. Leaders missed some slots, that’s it. The whole Ouroboros paper is about this.
Every Cardano epoch since the very beginning starts with a special block called “Genesis block”. This is not the same as the very first block ever, but kinda similar. Again, the whole original Ouroboros paper is about this. The whole point of epochs and the name Ouroboros is that each epoch is like a quick run of a simpler protocol. The naming is shitty, yes. But there’s nothing unusual. Each “Epoch genesis block” contains the list of slot leaders for the next epoch.
Again. There’s nothing to glue together. Some slots were missed due to an update and due to that smooth update system didn’t work that time. And then everything continued just like before.
