De mon côté j'avais cru comprendre que cette tolérance de fabrication impliquait un AF moins précis ;-)

Voici ce qu'on peut lire dans les FAQ de photozone.de :

"Q: What is the error margin for the MTFs ?
A: [...] Regarding the MTF tests the procedure DOES NOT rely on the camera's AF system which tends to be very unreliable.

Q: Will the resolution increase with new sensor related technologies ?
To some degree - yes. Assuming the manufacturers will find a way to get rid of the sensor low-pass filter there'll be a substantial gain for instance. Some lenses will also benefit from higher megapixels specifically in the center. However, a lens with a mediocre border performance will only marginally benefit from such measurements. Assuming optimal conditions I would guess that a few, very few lenses may have the potential to go up to 20mp on APS-C but only with their center portion."