I think both the OSU offense and OSU defense were still trying to figure things out earlier in the season. The defensive coaching changed was helpful, but I don't think they were a great unit. Stroud had a lot of overthrows in the first few games, and it seemed like he was a much better QB after he came back from injury.
The formula for OSU was pretty simple, try to outscore teams. The MSU game was an outlier as the OSU offense (and MSU coaching staff) took Walker's running out of the game early. OSU was susceptible to the run game all season. And like all defenses, if they can focus solely on either the run or the pass it helps them out. So score early and often, try to put the opponent in pass only mode, and on the flip side have the offense burn the scoreboard. That's essentially the 2021 OSU team.
So, depending upon what you think of OSU, sure, they could be overrated this season. I think part of the over/under ratings (in general) goes back to assuming everybody has carryover from the previous year(s) and way to early in the season rankings.