I believe that even top posters won't be able to make 10 constructive posts in an hour because we as humans need to have some rest after making some posts.
I guess it would depend on the strict definition of "constructive". If that doesn't necessarily include post length, 10 posts in an hour is not only possible but I think I've done it before and probably others have as well.
I don't think I've ever gotten that far, what I do usually write is about 5 posts in that time, which is when I usually connect during the week, sometimes it's in 50 minutes or an hour and 20 minutes. Or it's 4 posts instead of 5 but writing about a post every 12 minutes on average in an hour I do.
I was once accused of being a burst poster, which I didn't agree with, because to begin with I wouldn't be, but if you look at where I write (usually in the first or second page) and the quality of what I write, which without being top is not bad, and it was recognized by those who said that I was burst posting, it is clear that I am not. And precisely my manager, who is the one quoted in the OP, doesn't think I am either.