Obviously "overrated" is a subjective term. But I don't know that people are valuing the play-in by itself as much the chance to make the playoffs. As I mentioned before, playing the same team multiple games in a row is an experience the Spurs can't replicate easily. They can to test out adjustments in real time and get to see how players like Murray, Walker and Johnson adjust to a team game-planning against them. It's also at least five more Spurs games (because there's still TECHNICALLY a chance the Spurs get the eighth seed going into the play-in tourney), which for many fans is just a good in and of itself. That doesn't mean you're wrong about this stretch being a test for the team, but there are more tests they can also undergo, and I want them to experience more of them.
What's overrated is the downside to winning games. I think a lot of fans are under the impression that the Spurs making the play-in means the team they knock out picks above them. That's not necessarily true. The play-in only affects the draft order if a team makes the playoffs. The Spurs have the tie-breaks over NOP and LAL (and LAC even though it doesn't matter), and they'd make the play-in seeded above any of those teams. But the draft doesn't care about tie-breaks and reverts everything to coinflips. So the Spurs could get the eighth seed going into the play-in, lose two games and then still have the eighth slot going into the lottery. We're likely only talking about one slot in the lottery (at most) at this point. It's basically found money unless the team wins their way into the real tourney.