Sweeney did nothing wrong.
Normal ethernet ports can be pretty tiny, about the size as a regular USB port. It's a hassle for anyone not familiar with how they work.The new iMac models are less than half an inch thick. So, they could fit an RJ-45 port in, just, but it wouldn't fit behind the screen and whatever space it took up in the chin would be effectively dead space. They give the same reason for the exclusion of USB-A ports, though that's considerably less of an issue than RJ-45 would be.