What version are you running, I think early version of 7 had issues, but with 7,.4 I know it works fine. WHen you put the host in maintence mode the vms are migrated and then the cp-parent vms are deleted. The instant clone can move as long as there is a running cp-parent for that pool is on that host I believe. In older versions I think you needed to use these
We have Horizon 7.5.1. I'll try in test environment.