What I am saying is why I can select the nodes in the storage but not in the job backup?You're saying you do not want VMs to run on that node, correct? If you already have that set in the HA settings then that is what will happen.
Now, I'm not sure why you're saying you don't want the backup storage to be attached to that node, because, again, nothing will run on it anyway, so it does not matter if it's attached or not. It will not try to backup anything to the storage, because there's nothing back up to it. There is no harm in having this backup listed attached to that node, unless for some reason you're worried that someone will restore the VM to that node.
I couldn't see no reason why not.