Yes, it does, and to expand just a little - the same guesting restriction would apply in the BA lounge, even if you’re travelling BA F. There’s no prospect of guesting someone on a Star Alliance flight anywhere.

The restriction Prospero mentions just seals the deal. You could, technically, sit in either A or G side with your friends and then re-clear security (the TSA does allow any BP to go to any terminal), but that’s almost certainly not worth the aggravation, particularly as Concourse A - even in Fast Track - can take a while.