If he's successful with Twitter it will add credibility to the idea that most high margin SaaS/social companies don't need as many people as they currently have

If he's successful with Twitter it will add credibility to the idea that most high margin SaaS/social companies don't need as many people as they currently have, yes. And they certainly don't from a theoretical perspective. Whether they can successfully transition from inefficient+large to efficient+small is another question