My quick read of the Behr piece David posted was that he was against the difficulty of the numerous bunkers and outright difficulty. It almost sounds like a modern scenario to me - USGA hires well known architect, but has definite ideas of their own.
The reality was quite the opposite. Behr wasn't against the difficulty. He viewed the course as as an outmoded pushover, a "dark ages" relic, despite the addition of the bunkers. Same for Anderson.
It would be nice to have been a fly on the clubhouse wall to hear those discussions. Maybe it really didn't look like typical Ross at all. 45 years later, Ross' plan to toughen Oakland Hills looked a lot like what RTJ implemented, so I figure the USGA had a lot to do with that, as well.
As someone suggested, I wonder how the tastes of the times might figure into this - were they trying to elevate the open? Embarrass the pros to keep the amateurs looking relatively good? The mind spins with possibilities.
I think you are reading modern scenarios into a situation where they really don't apply. The US Open had never been a big deal until right around this time, and as Greene suggests, the choice of courses had always been basically an afterthought. It wasn't like the prestigious Amateur where the best clubs took pride and honor in hosting. But with McDermott's two wins then Ouimet's win at the CC over Vardon and Ray this all changed, and suddenly the tournament meant something. This was the first Open after Ouimet's win and the USGA apparently put on a last minute blitz to try and get get Midlothian up to an acceptable standard for what was becoming a "major" tournament, but according to Behr, Anderson, and Greene, they fell short.
Midlothian's situation was not all that different than about every other course in the country. The Golden Age had arrived. There was a new approach to golf course design and virtually all of the courses were significantly altered to try and catch up.