A couple of factors that make the yardages a play bit closer than 600 yards:
1. Olympic Lake for US Open is a par 70 (par 71 for members) vs. ANGC par 72
2. Heavier San Francisco air given Olympic Lake is right next to the Ocean and gets the dense fog - and subsequently less roll.
When the Lake is lengthened for the Open, it may very well play as long as the current ANGC. Probably by then however ANGC will be 8,000 yards
How about uphill holes/shots? Olympic has quite a few, doesn't it? They can add a lot to playing length. And downhill shots make a course play shorter. How do the two courses compare there?
Seems to me we should take rough into consideration too. Heavy rough normally makes a course play longer. More irons/fairway woods off the tee. Longer clubs into the greens out of the rough, and plenty of chopouts that turn par 4s into three shot holes.
These points make 17 at Olympic especially diabolical during the open. Real, real hard to hit that sloping fairway. Equally hard to hit the green from the rough. The entire hole is uphill, adding more to its length. For all these reasons, 17 will play way way longer than 470. Longer, e.g., than either 10 or 11 at ANGC?
One way to compare "playing length" off the tee, might be to look at the average drives during tournament play on each course. To keep things even, take only those golfers who play both events. Say during the Masters they average 295, while at Olympic during the U.S. Open they average 275. With 14 driving holes, seems to me Olympic just added 280 yards in playing length, on drives alone. I'm making up the numbers, though I bet the pro's do average longer at ANGC.