The whole reason for the change? Righto. Let me tell you what REALLY happened during maintenance.
So, High Overlord Saurfang was chilling out at the laundromat, because sitting in the middle of Orgrimmar and sticking dragonheads on sticks is pretty messy work. All the dust and blood can really accumulate, you know? So, he's there sitting in his loincloth reading the "How to serve man" section of the Orgrimmar Weekly and chatting to various lady-grunts that are there also getting their uniforms cleaned.
Washing machine finishes, but he realises that some new driers have been put in. He sticks most of his armor in one, but can't fit the shoulderpads in. Annoyed, he puts them in a separate dryer without realising that the temperature is on a couple of settings higher than the rest of his armor.
So they shrunk.
Rather than going to Molten Bore and beating up the fools in there to get a new set of shoulders, he put the shrunken ones on. There was only a few minutes before the server came back online anyway, so he was in a hurry to get back to his place in Orgrimmar in case someone bought him some heads to pike up.
Since Saurfang is a celebrity amongst male Orcs, they all adopted this new fashion so that they would not outshine Saurfang in the way of shoulderplates.
Saurfang is currently building a bridge from Orgrimmar to Blackrock Mountain with the skulls of people who defend the cave of AV. Once complete, he'll walk into the Molten Bore and demand a new set of shoulders from Sulfuron every week.
Knowing how reliable Sulfuron is, Saurfang will probably be peeling Vendorstrike from Sulfuron's corpse for a couple of weeks first.