When I toured Mills River they were brewing Pale that day. The hops listed on the dry marker board were not the ones on the web site. That was mentioned online by others. This was added to the ingredients list around that time-
"Brewing is as much art as science, and all beer specifications and raw materials are subject to change at our brewers' creative discretion."
Other beers have improved through process changes. On a Bell's tour they said a brewer had hired on from another brewery, suggested some changes to Lager of the Lakes, and it was a noticable improvement. Don't ask me what was changed, don't know.