The schematic in the instruction manual shows the EV connected directly to the combination valve, which is what he has done.The vessel is not in the correct place to take up expansion.
The installation manual will give you concrete evidence.
An easy mistake to make but best to check they have the correct qualification.
The combination valve is made by Reliance, but unfortunately I cannot find the model, to confirm what the inlets & outlets are for.
Should the EV have been connected to one of the outlets on the left instead?