I get why Scar is portrayed as the more 'social' one between himself and Grian. Scar is friendly and bubbly and charismatic, and people tend to run with that, whereas in some (particularly life series) Grian characterizations, his snark and tendency to complain about his teammates gets interpreted as Grian being less attached to people and generally less socially aligned.
..The thing for me, though, is that Grian's way more socially dependent than Scar is.
Now don't get me wrong Scar likes people, his charisma is one of his best traits, and he does prefers to play toward having a team over not having one. It's a running theme, actually, in the Life Series, where Scar will end up alone because, while he does hypothetically want to be with people, it's never a huge priority.
Last Life comes to mind, where Scar, despite complaining about not having allies, actively keeps his allies at arms length and rejects alliance deals. Or Double Life, where Scar thinks about everything but finding his soulmate for the whole first episode. Or Secret Life, where Scar actively rejected whole alliance offers because he didn't want the commitment (his words) in the early game.
Grian, on the other hand, cannot survive without people. He makes sure he is never alone. Grians "team hopping" gets pointed to as disloyalty, him seeing people as disposable, but to me it reads more like desperation. Clinging to Joel after having to leave his team in Last Life, hovering around BigB when Scar shows limited interest in him during early Double Life (also the way grian subtly romanticized soulmates in his first episode was sweet and very telling), immediately team swapping to the Nosy Neighbors after his team died in Limited Life, doing the same thing and jumping into The Family after his team died in Wild Life..
I think the best example though is the one time Grian was alone for any real margin of time. Secret Life. Grian was alone for a few episodes and it had a noticeable negative impact on him, to the point where he was throwing himself at Joel and practically begged Etho and Cleo to keep him around. At this point in the same season Scar had rejected alliances and was relatively happy playing solo without the commitment of a team.
Scar is extraverted in the sense that he enjoys being around people and has a lot of fun with socializing. Grian is socially dependent in the sense that I think he'd literally crawl into any of the other lifers skin if they let him.
(to be fair..scar is a cat and grian is a parrot. cats are facultatively social animals who can adjust to both group and isolated living. parrots are highly social animals who absolutely need daily interaction, as in, they can develop severe depression and anxiety if they don't socialize for even one day. so. checks out, i think.)