Two reviewers can drive the same vehicle, report accurately, and disagree completely. The usual explanation is not bias but geography, because the test route decides which qualities are exercised.
Roads select the qualities that get tested
Suspension tuned for compliance over broken surfaces feels sophisticated on poor roads and slightly loose on smooth ones. The same setup produces two different verdicts.
A short-geared engine that feels eager in town becomes busy at sustained motorway speed, and a reviewer who never leaves either environment will only ever meet one half of the character.
Neither reviewer is wrong. Each has measured a real property of the vehicle against a road that happens to reward or punish it.
Launch routes are chosen by the manufacturer
First drives typically take place on roads selected by the company that built the vehicle, which naturally showcase what it does well.
This is not usually deception. A manufacturer that has developed a machine on demanding mountain roads will choose demanding mountain roads, because that is where the work went in.
The consequence is that early reviews cluster around the same impressions, and it takes independent testing on ordinary roads before a fuller picture emerges.
Surface, weather and traffic distort measurements
Performance figures are sensitive to ambient temperature, altitude, surface grip and how much fuel is aboard. Two tests conducted properly can produce numbers that differ noticeably.
Fuel consumption is more sensitive still. A route with a long descent, light traffic or a tailwind can shift a consumption figure enough to change how a vehicle looks against a rival.
Reviewers who quote figures without describing the conditions are offering a number that cannot be compared with anyone else's, however carefully it was recorded.
What makes a review portable
The useful reviews describe the road as well as the vehicle, so a reader can work out whether the conditions resemble their own.
Comparison tests are more transferable than single drives, because the same route and the same day apply to every vehicle, and relative judgements survive even when absolute ones do not.
A reader's best defence is to read several reviews from different regions and look for the observations that recur. Traits that appear regardless of route are properties of the vehicle rather than of the road.
Duration matters as much as distance
A route long enough to produce fatigue tests things a short drive cannot reach, including seat comfort, wind noise at cruising speed and how tiring the controls become.
These are the qualities owners complain about most and reviewers report on least, because a two-hour loop simply does not run long enough to expose them.
Extended tests conducted over months therefore tend to contradict launch impressions, not because the early verdict was wrong, but because the route never asked the question.