That would be due to the players playing from a tee box that matched their skill level(Tee box issue). Basically no one else plays from those distances. Also, the US Open is going to be one of the, if not the, toughest scoring layout those guys play all year. It's nothing like what they play week in week out.
Oh, THAT's the tee box issue? That's the same as "we should just design better holes", right?
I don't think anyone disagrees that having players always play from tees/holes that are appropriate for their skill level is the ultimate goal.
I recognize that it would be a lot easier to set par in that world. For designers who, say, successfully set out to create only holes with normal (like 25/50/25) scoring distributions, it is obvious what par should be. And, design flows from the intended par.
That leaves three practical issues to clean up. One is that the hole won't always play the same as it was designed. Most often players will find an unnoticed shortcut. Then, if the hole can't be redesigned, we need a consistent way to decide what par should be for the way it actually plays.
Another is that even when holes are well-designed for a skill level, some TDs or designers may have various notions of what par should be. Or, they may be targeting more obscure scoring distributions (50/0/50 is a popular one for island holes). We need standards they can follow.
The third is that the top players won't always be playing on appropriate holes - at least not for a while. For those holes, we need a way to set appropriate par. Since we have methods that reproduce the pars for appropriately designed holes/appropriate tees for both disc golf and golf, we can use those same methods to set pars for inappropriate tees and holes, too.
Merely setting appropriate par doesn't solve everything - and it is not a substitute for improvements in designing and using appropriate holes, but at least par can start doing what it's supposed to do in the meantime.