Who says it's not an issue? I think it is an issue.So why isn't this an issue for FCS teams. They have had a 8 team playoff for years now.
If FCS can navigate these issues, it stands to reason FBS teams can do the same.
However, even if not, there are some distinct differences between FCS an FBS. The FCS play 12 games a year and most have no conference championship. Also, they start their playoffs immediately after the season and finish about the same time as the FBS. Last years FCS Championship game was played on 1/11/20. This years FBS Championship was played on 11/11/21 - same month and date. Unless they change the current scheduling system, if you add 2 additional games they would not finish until the second week of February. That is a very distinct difference.