As an observation ; I'm going to draw attention to @majorp93's point about rebooting the servers after ALL nodes have been upgraded.
Historically we would move all VMs off master, upgrade master, restart its toolstack, then reboot master, then move VMs from Node 1 to master so we could begin the upgrade on Node1. Normally works ok but last time around it caused all sorts of problems. Previously it had felt right to upgrade master in its entirety including the reboot before moving on to the next host and rinse, repeat - but this cost us a lot of time, corruptions and pain.
TLDR: Perhaps add a footnote to the docs that when upgrading a pool the reboots should take place as a final step across the pool only after all nodes have been updated.