With 3.6 the engine is able to auto-import the hosted-engine storage domain into the datacenter. At that point the hosted-engine storage domain will be connected to another storage pool.
hosted-engine-setup fails connecting the storagePool cause it has just the uuid of the boostrap storage pool which is not actual.
Avoid connecting at all the storagePool from hosted-engine-setup on additional hosts.
hosted-engine-setup is able to deploy an additional host.