I honestly can't figure a reviewer listening to the entire set, let alone making comparisons. I'd bet he sampled here and there (he does say he had trouble finding individual works because of the chronological numbering used).
Why not? A musicweb reviewer did just that for the Fischer cycle. Reviewers have done that for Haydn's SQ, PS and PT box sets. It's important because many times the performer changes his/her approach to the music as he/she progresses to more mature works. His review does not indicate that he did any kind of sampling, just that he didn't like the packaging and organization. He makes almost no specific comments about the music making itself. Don't defend Hurwitz here, he did not post a real review, he simply took an opportunity to slam a conductor that he clearly has a grudge against.
Edit: besides you've straw-manned my point. It's not a hardly listen vs completely listen, that's a false dichotomy. I was clearly saying that he should have listened to more than just the first cd. His specific comments suggested that is all that he did.