When you're talking about half the lineup's worth of positions(OF+1B+DH), if you have one person per spot you're actually short. If you have 6 players for 5 spots you've got an average of 135 games per person, a very reasonable target. Case in point, we're 120 games into the season as of tonight, and Seiya & Bellinger have missed 30 games each. Throw in 10 games each(at least, given Busch and PCA's uncertain platoon strength) for the other 3 spots for rest and matchups and you've got a near full time work load for someone. Also players can have long term injuries, pitchers could figure out PCA or Busch and make them unplayable, etc.
What this does do is make it a little bit harder to convince certain players to join your project. Juan Soto won't care, he's at the top of the food chain no matter what lineup he joins. But any bat-first FA they approach might have second thoughts about how long they'd be allowed to work through any struggles. That JD Martinez/Anthony Santander caliber of player that may be a fallback(or primary depending on other moves of significance) is the type of guy who may go elsewhere so he doesn't have to worry about a PCA breakout ruining his ability to get another contract.