Several regions present their newest wines to critics months after harvest, long before those wines are finished. The assessments that follow are useful, and they are measuring something different from a finished bottle.
The sample is not the wine
At the point of tasting, a vintage typically exists as separate lots in separate vessels rather than as a single wine. The final blend has not been decided and often cannot be yet.
Samples are assembled to approximate the intended blend, and the proportions may change before bottling. A producer is showing an intention as much as a product, and intentions move.
The wine will also spend a further year or more in barrel, during which tannin polymerises and oak integrates. Both processes alter it substantially.
Young wine misleads in specific directions
Unfinished red wine is typically more tannic, more oaky and less integrated than it will be at release. Those characteristics dominate the impression.
Primary fruit is at its most obvious, which flatters wines built on immediate appeal and disadvantages structured ones.
Experienced assessors compensate by weighting structure and balance over immediate pleasure, which is a projection rather than an observation.
Sample preparation introduces variation
Samples drawn from barrel are handled, transported and sometimes held for days before being tasted. Each step changes the wine slightly.
A sample drawn well before a tasting behaves differently from one drawn that morning, and practices vary between producers.
Where samples are shipped to reviewers rather than tasted at the property, transport conditions add a further layer of uncertainty.
Ranges rather than points
Most reviewers publish barrel assessments as a range instead of a single figure, which signals the uncertainty honestly.
The width of the range is itself informative, since a narrow one indicates a wine already showing clearly and a wide one indicates a wine that could go several ways.
Converting the range to its midpoint, as many retailers do, discards exactly the information the range existed to convey.
Why the system persists anyway
Early assessment supports a trade in wine sold before bottling, which funds producers during the ageing period and lets buyers secure allocations.
The scores are the pricing mechanism for that trade, so their existence is commercially necessary regardless of their precision.
Reviewers who retaste at release and publish the revision are doing the part that makes the earlier number defensible.