If they are standard paving blocks, eg Marshalls Keyblock or similar, then it is not possible to lay them with tight joints. They have little ridges on the sides to ensure even sized joints (approx 3mm).
They are laid the right way up with the chamfer on top for a reason. Block paving is designed to be “flexible” and the 3mm sand joint is there to allow movement.
I’d be wary that they guy suggesting that they can be laid upside down doesn’t know what he is doing.