This whole thing makes no sense to me.
For argument's sake, lets say that there are 124 golfers in the US Open the first two days and the two practice rounds. That adds up to 31 foursomes, and if they tee off 10 minutes apart that would be five hours of tee times. Caddies are a non-issue as the caddies are needed for walkers in non-tournament conditions, as well.
During the final two rounds you'd have 60, plus ties.
On busy summer days in regular season, I can imagine traffic much heavier than that is routine. I would think that members and their guest would be teeing off from 7am til 5pm throughout the season.
Are those arguing that there isn't time for repair saying that today each green at Merion East uses 7 or more hole locations in mid-season to avoid problematic wear?
I think Jamie's post above is spot on...as someone who has played Merion in top competitions, I think his opinion is quite credible and valuable here.