I disagree with this in bold. Precedent is important here. Like others have said, it is a risk vs. reward calculation. A lot of other draft picks sit out bowl games - it is the norm. But if you were to decide to sit out half the season or even a few games, you would stand out from the crowd and might get something about it on your draft profile. Up to a point these guys have to show to scout that they are team players and can show up to work and play through things. Right or wrong, that standard ends at the regular season. Because lots of other team players like Bell and GK have done it, it is not a red flag in the least.
Also, draft position isn't 'secured'. There is still the combine, which is less than 2 months after the bowl game and for which these guys are currently healing up and preparing for. That is now the single most important thing left for these guys to get drafted high.
Let's not overuse the slippery slope thing here. There is a very clearly defined line between regular season and bowl season. And that line is holding. We even made it through Covid and the 'opt out' culture without much impact on where that line is. If someday it becomes the new norm for guys to quit on their teams halfway through the season, I'll join in this concern. But as of now 99.9% of the players are staying committed further into the season than the coaches and administrations.