Hmm, if the the company president say "It's a lost art," I would suspect the sound of this new crop 300B are yet different from the old NOS 300B.
Unfortunately this paragraph are even worse:
Whitener's company sells a handful of different models of vacuum tubes that are exact reproductions of Western Electric "classics," such as the 300B tube that originally was used in movie theaters.
Seems they are unaware the original NOS 300B and the 1998 WE 300B sound different.