I have adopted seven greyhounds over the years and fostered a half dozen more, and never had one with a severe case of SA. Not saying it doesn’t happen, of course it does, and maybe a little more often in greyhounds than other dogs just because greys are so used to being around a bunch of other greyhounds their whole life. Many greyhounds (and other dogs) are nervous in new, confusing, different surroundings but this wears off in time. We say the dog you have in six months will not be the same dog you brought home, as their personality blossoms.
I think getting two at the same time is a good idea if you have the finances, room, etc for two, they usually enjoy the company. I have heard of animals that form a strong bond with each other, but never heard that they couldn’t/didn’t form a strong bond with their people as well. Love is not a finite resource
All of these comments should be read with an implied “often” or “usually”, because obviously, each dog is an individual.