I think Halliday / Wine Companion leave plenty of headroom from their own point of view; the problem is with personal preference; inconsistency of the taster's sensory experience from one day to another; and in some cases, bottle variation too.
As far as headroom goes, the scale is clearly not linear at the top end. I mean, if you look at what they have in the current book year on their website, there are 3,493 wines, of which one, just one, scores 100 points, seven score 99 points, thirty-four score 98 points. So only 1.2% of wines tasted score above 97 points, and only 0.2% above 98 points. (There were 234 with 97 points though, which by itself is 6.7% of the total. This just emphasises to me how closely they guard those top three ratings.) Turning it around, one in fifteen wines they taste gets 97 points, one in a hundred gets 98 points, one in five hundred gets 99 points. One in, well, 3500, gets 100 points.
So it certainly seems they are reserving those top three spots (98, 99, 100) for what they think is truly exceptional. Of course, given personal preference, you and they could have opposite opinions on what you think is exceptional. Never mind diurnal taste bud anomalies. We should remember that wine reviews can not really be much more quantitatively precise than music reviews. They are just a useful guideline, and often the text of review is a lot more important than the score in deciding whether you'll enjoy a wine. You've gotta know if it's disco or classical, or heavy metal. Which is why it's so helpful to have a forum like this to help us find the relevant reviews for these mystery wines.
