The problem with assuming that there's no referee bias because referees don't go into games intending to favor Team A over Team B is that it assumes intentionality is necessary for biased calls. It isn't.
Alabama vs. LSU were prime examples over the years. Many LSU fans thought referees were in the bag for the Gumps, and eventually the issues were obvious enough to grab the attention of media who openly questioned calls. (The same media who likely created the problem I'm about to describe.) Personally, I don't think the referees ever tried to tank LSU's games against the Tide. I think referees are people like the rest of us who are subject to the constant barrage of "information" on certain things, and like the rest of us, it can't help but color our opinion. The studies of the effects of propaganda on people who know they're being inundated with propaganda are clear. Even when we're aware of it, it affects us.
So when Alabama's OL has a reputation for being amazing and they are amazing without having to commit holds, does a referee have to be in the bag to miss holding calls? I don't think so. But believing without realizing it that this OL does what it does without holding may lead to seeing something that makes you say "Was that holding. Eh...it was questionable, I'll let it go."
I've said this a number of times as an illustration, but also to show I'm attempting to not be biased, I think the same thing was true of LSU DBs for a long time. For a decade, LSU was considered DBU, or one of the DBUs at least, and not without reason. But I noticed that our DBs got away with more grabby behavior than other teams got away with, and earlier contact with WRs than other teams got away with. There were many times our guys made a "good play" but I was convinced there was no flag because refs were used to not throwing flags on our DBs. It didn't have to be "I'm rooting for LSU so I will not throw a flag." Maybe it's more "These LSU DBs keep going high in the draft and becoming NFL stars and they're so well coached, look how they defend right to the edge of what's allowed." When maybe sometimes it was just PI.
Granted, Alabama seemed to have more instances of that working in their favor, but I'm just pointing out how narratives affect calls. I doubt the officials were intentionally biased toward UGA, but I raise my eyebrows when calls start getting a certain amount lopsided. UGA is the team now who loads the NFL with stars and has recently won two NCs and has all the narrative about it's great staff, coach, players, etc. I think it's naive to believe that has no effect on the referee crews. And the no-call on the late hit on Ewers was flat-out egregious, nobody but the homerest of homer UGA fans could say otherwise. I don't recall if it made a difference. But it was a horrible no-call on an obvious PF.