I'm inclined to agree with Amber and Redhead.
Merlin is lazy. In the winter he literally hibernates and goes from his bed to the couch to his food bowl to the yard to the couch to his bed. There have always been walks, regardless of the season, but more for the mental stimulation and the socialization than anything else. On the other hand, I don't think that Sagan would have been happy if he couldn't have run off-leash. He LOVED it. Not so much when we used to go to playgroup years ago - he would sniff and stick close to me - but when we went to the (totally enclosed) beach or to a ballfield for a run. Not only did he love it - it also transformed him from a shy, extra cautious hound into a curious, adventurous hound with a greater independent spirit than he ever had before. It was so wonderful to see.
I will always remember how happy he was when I took him for a run. He could hardly contain his excitement.
If I'm perfectly honest, I don't like the idea of a dog - any dog - never having the chance to really stretch their legs, but I do agree that it depends on the dog. After all, some people don't even walk their greyhounds, and in principle I don't agree with that at all, but honestly, some greys are just so low-energy (okay - lazy ) that they seem to be perfectly fine with pottering around the yard and doing zoomies for five minutes. So I think we need to be careful about projecting our human preconceived ideas onto our dogs. I know I've done it! Every dog is different.
Good luck!