Sorry to be the odd one out, but I think the OP has a point.
if you are flying at a flight level, the QNH is not a mandatory item, as it's not an altimeter setting in that case.
When ATC descend you to an altitude, they will give you a QNH and then it becomes a mandatory readback item.
So IMHO when inbound at a flight level, the ATIS code is sufficient, no need for QNH.
Whatever the company SOPs decide to do with their standby altimeter, it's got nothing to do with ATC mandatory readbacks.