"I do question letting critics see the shows before opening night. It gives them more time to craft and ruminate, whereas if they just saw the opening night show and were on deadline to write a review, they would actually write about what happened onstage, no?"
It cuts both ways. Sometimes you do want a critic to ruminate and sometimes you just want an immediate response.
For example, Frank Rich saw Speed The Plow and gave a decent review to Madonna. After many people wondering what Madonna had done to Rich to get that review, he had to walk back his review and admit she wasn't as good as he had originally thought.
Plus I also wonder if there is wisdom in reviewing opening night. The production team has pushed so hard to get a show open that many times opening night is running on sheer adrenaline and may not be a representation of the show once it settles in.
If anyone ever tells you that you put too much Parmesan cheese on your pasta, stop talking to them. You don't need that kind of negativity in your life.