That's because they're a huge international airline and they have to keep things kosher.
GS is a special invite status reserved for celebrities and high ranking politicians. My assumption is that they need that space so that they can load the person from the tarmac or have them check out of the airport. Thats speculation, but those individuals do have different needs from an airline. [Also onboarding needs as well as that they don't enter from the jetway]
GS folks board normally, though sometimes will get called by name to board first. GS is invited essentially on revenue only (though perhaps special people have special handling). If your spend is above $50k, you probably have a fair chance of getting invited to GS.
GS is a special invite status reserved for celebrities and high ranking politicians. My assumption is that they need that space so that they can load the person from the tarmac or have them check out of the airport. Thats speculation, but those individuals do have different needs from an airline. [Also onboarding needs as well as that they don't enter from the jetway]