It's not that one or two games though - it's the whole process of going for it, improving after the trade deadline, playing a lot of close games, hitting game winners, missing game winners - all of that. As opposed to being shut down for the season after game 60.
Also, it's not like the Spurs have traded for a bunch of veterans in order to chase the play-in - they have done the opposite - they have one guy who's 28 in the rotation and everyone else is younger. Even Primo, who's the youngest player in the league and is super raw, is close to hitting 1000 minutes for the season, which is more than Murray, Keldon and White have played in their first seasons combined.