Don't forget that a Greyhound is a very different breed than the Azawakh or Sloughi. A greyhound is a sprinter, with more 'bulky' muscles, just like a Whippet. They won't show their hipbones as fast and prominent as a long distance runner, like the Azawakh or Sloughi, that have very flat muscles.
And I rather see a bit too much rib than dogs with too much fat. Certainly because an owner quickly thinks his/her dog is skinny.. when it isn't.. Lots of owners totally miss the fact that their dog can loose some pounds :S
Here a couple of Azawakhs that we met at the European Lure Coursing Championship
They show ribs as well, but in my opinion, they are not too skinny. And I don't think their owner will starve them to make them look like this.. because it wouldn't help with LC
I showed some pics of Tillo in the other thread, and a lot of Basenji people I meet think Tillo is too skinny when he looks like that.. I can't understand it :S