Sorry to be negative but ...
They all make their own rules! There are many, many 'standard' sizes. If the CC thought that, in an emergency evacuation, your bag would have caused you, or another pax, to trip as they left their seat - then that is that and you accept or leave the aircraft.
You will never get a clear answer on this. All the airports point to the airlines and they point to their standards. If there is an anomoly between the 'standard' on one sector and on another - even with two aircraft of the same carrier? That's the way it is. The CC have to secure the cabin the way that they can defend to their manager of, worse case, in court.