Dude, he like, literally, answered some of the questions you're asking in this post in the post you quoted.
You are right about one thing, though. If you're already working with an instructor, you shouldn't be muddying the waters with advice from other sources. In fact, Erik and Mike make points to not offer advice when they know that, so you should have just mentioned that from the start.
I have a friend who is also on Evolvr and got feedback today from his coach that his swing is looking great and has no changes at this time.
I looked at his swing. He goes from really shallow at A3 and then slightly steeper at a5. Why is that ok for him and not for me? Seems a little hypocritical, eh?
Still a shot for the top 3 players in the world to all have won the last tournament they played at the same moment in time, which I don't believe has ever happened in the history of the game. #pgatourhasneverbeenbetter
Ok, that hash tag was a little douchy, but c'mon, this shit is good.
But because they play on courses that are considered quite difficult compared to the average home course, wouldn't their up & down % be expected to increase due to having closer misses on average - particularly with slower greens to hold approaches?
The comment above is not to discount this, but only emphasize how the two go together. If you apply a fantastic long game on a shorter course on average they will have an easier time being more consistent and hitting the ball closer to the pin on average and therefore making more putts. Or do you think they would have the same expected proximity on one of our home courses as they would on the tougher tour courses and setups?
I get you on the tournament prep being very different to hitting a course blind, but to some extent the OP is comparing how we play on our home courses day-in, day-out vs. the tour pros moving from place to place. How would we score visiting a course blind relative to our home course where most of the scores are posted and we are very familiar with the layout and greens. Granted pros make it a point to know this stuff with yardage books and memory. Still switching between venues and conditions rather suddenly vs. gradual changes we would tend to experience on a home course must add some difficulty.
I came across a good study that analyzed all PGA tournament scores for 2007 including field average adjustments. He had the unadjusted scoring average that year as 70.704. If you figure the average course setup is ~ CR 75 and add one stroke for 'tournament conditions' (and added difficulty of Major setups) then that was about 5.3 strokes below average rating.
So relative to a Course Rating (slope should not matter to a pro), and assuming a standard normal distribution, 95% of the scores should range between -6.7 and -3.9 below the rating. However, his analysis detected two interesting features, the curve (with a ton of samples) is approximately symmetric with a ~ .4 skewness. This right skew means the most frequently expected result (the mode) is actually slightly lower than the mean. So that implies that even on tour setups the lower than average scores are expected just a bit more frequently (the left tail and shoulder are slightly thicker and probability for scores lower than the mode slightly higher.). Here's an approximation of what the distribution would look like relative to strokes below the CR.
In comparing courses with higher average scores (like the U.S. Open) the study found that the standard deviation of scores increased. The 'tougher test' created more of a separation between the players. Also the players whose scores tended to skew left were poorer players on average in terms of results. They averaged a relatively high score, but they could go really low sometimes.
The relevance this has to the thread is that on the easier home courses that most of us tend to play, the tour players would be more bunched in their expected scores with higher probabilities around the mean of -5.3 relative to the CR and possibly more toward the low side with the left-skewing, less-consistent scorers reducing the size of the right tail and extending the left while holding the 'field average' the same. It could skew the distribution toward lower expected score (though the most frequently expected value would still be around the mode).
But what would you expect as a total spread for the average scratch population? You agree that with the average population of golfers by handicap there's a decrease in score variability with increasing skill versus the average population at each handicap level having the same average scoring distribution, yes?
IMO, the answer to the OP greatly depends on the CR.
On my course from the tips, they'd be expected to shoot under 65 over 50% of the time. On a CR of 72, I'd expect below 67 over 50% of the time. At Oakmont (in non-Open setup), under 73 over 50% of the time. And that would be without accounting for a possible 'going low' effect from the typically easier home course setups we face (not including Oakmont there. They would face some hazards you don't find on tour either - lost balls could be an issue for some.
I'm not sure I agree that they'd expect to putt worse. At the least because I would expect their proximity to the hole to increase on all shots due to the typically shorter length (shorter irons on average into each hole) along with relatively slower, softer greens.