My guess is that one of the reasons for the disagreement between George and Mark is the different definition/ description of the term "playability" that they bring to the table.
If as an average golfer I played Oakmont from the appropriate tees and had my average/typical round of ball striking, chip/pitch/bunker shots and putting, I'd fully expect my final score to be higher, perhaps much higher, than it is on my home course.
But with that as a given, I also imagine that if I focused on and somehow managed to stay below the hole on those fast greens, and thus limited somewhat my number of 3 putts, it might not be exponentially higher.
Now, if I had a below-average driving day (and was very often in the rough/bunkers) and/or if I didn't stay below the hole on most of those fast greens, and had not only a whole bunch of 3 putts but also some 4 putts, my score would be exponentially higher.
I wouldn't like that so much, and I'd probably feel a bit embarrassed at my very high score, but I'd know what that exponentially higher score was built upon, i.e. rough/bunkers and length and hard fast greens.
And, as an average golfer, I wouldn't blame the golf course for that, I'd blame myself. I'd think to myself: "If I'd hit a few more fairways and if I stayed below the hole, I would've score higher, maybe much higher, than I do back at home, but not exponentially higher. That I did so was my fault, not the course's".
And I can imagine -- maybe like George can also imagine -- coming off the 18th green and thinking "Wow, that's a really hard golf course, but it was indeed quite playable".
And why would I say that? Well, in part because I'd just finished playing it. But also because (to come full circle to my opening line) I'm a dedicated but average golfer -- and dedicated average golfers tend to think that way.
Good golfers don't think that way. They have a different definition for and experience of "playability".
Peter