So in this case, knowing that he mills it himself and that he seems to use old school methods, in addition to just baking great bread is a recipe for a better bread experience than that of simply eating great bread without knowing the story.
Even if you have neutral perceptions of sandwiches you will definitely taste the difference between American bread and European bread.
By grinding the grain in the bakery, it avoids the processing. The baker has to adjust recipes on the fly to adjust for the different gluten/protein levels since that will vary.
That might account for taste difference. Double blind trial would be interesting with different flours.