I'm not gonna pretend to know how the attribute works, but I do wanna throw my ideas out for other "big time" games, both college and pro.
College
Rivalry Games - Either Designated or with some sort of "recent history" metric, maybe with a historic adjustment so that you have default rivalries, but they evolve over time. Like OSU-Penn State blossoming into what I always thought was a rivalry.
Ranked vs Ranked - Both in-conference non-rivalry ranked games and non-con ranked games tend to have pretty raucous atmospheres. To me, that's what really defines a "playoff" atmosphere: how much the crowd cares about each individual play. USC at Ohio State, Texas at Alabama, Oregon vs whoever wanted those hands, always made the game feel very important. I think the players buy into it as well.
College GameDay Location - You got picked! You're in the spotlight! Now live up to the hype!
Pro
Divisional Games - Steelers vs Ravens, Seahawks vs Niners, New England vs everyone else. The 6 games against your divisional opponents are your rivalry games in the NFL, so the extra fight and strategy comes out these weeks. No matter how good the Bengals are lately, the Browns still beat them, and that's because Baker Mayfield was Clutch AF.
Week 17, 18 Games - IFF both teams are in the hunt of the playoffs and/or seeding (not eliminated or locked into the 1/4/5), both teams are fighting for their lives. These are the pseudo playoff, playoff-in games. Given these are also rivalry games, it gets extra spicy. Negated if one team rests starters.