Of course if you had two PVE hosts configured the same using PBS in a CT container then you could backup to either PVE node and then remote PBS sync to the other one and have pretty good two node backup redundancy. Even on a single node, the ability to "freeze" a VM/CT by backing it up to PBS (and removing it from PVE) then be able to one-click restore the VM/CT is very handy.
Of course if you had two PVE hosts configured the same using PBS in a CT container then you could backup to either PVE node and then remote PBS sync to the other one and have pretty good two node backup redundancy. Even on a single node, the ability to "freeze" a VM/CT by backing it up to PBS (and removing it from PVE) then be able to one-click restore the VM/CT is very handy.