I don't think posting -4 vs. +5 or 276 vs. 285 tells us anything about whether the course was fair or not. They were the same par (71) but Oakmont and Winged Foot were, on the card at least, almost 300 yards longer than Shinnecock. That's probably the biggest factor in the scoring discrepancy.
If you're of the mind that what we saw at Shinnecock was problematic, I thought the 10th was more problematic than 7. It seemed that no matter what kind of shot the player hit in there - good, bad, low, high - the ball wound up over the green. We can always argue what 'fair' means, but when there seems to be no way for a well-played shot to get an appreciably better result than a poorly-struck shot, then I think we're pushing the limit. Maybe it's not a fair vs. unfair question, but while golf is full of odd bounces and breaks, it seems that a well-played shot should have a good chance to get a better result than a lesser shot. I don't recall seeing that on the 10th at Shinnecock on Sunday.