I think you'll find the reason may be because, when it's not set up for the US Open, it is probably a par 4 for the Pro's (back tees) and a par 5 for the members (forward tees).
There is a similar hole at The Belfry in the UK where the Ryder Cup used to be played. The 10th hole white tees (back tees) is actually further forward than the yellow tees (for normal day-to-day play). This is to encourage the pro's to try drive the green.