Actually, what that webpage shows is a scan from a page of the Enterprise's "Biography" that Lincoln Enterprises sold. The biography was based on the original writer's guide, publicity material produced by the studio, and artwork provided by Matt Jefferies. It was written/assembled in late 1967/early 1968.
Robert Comsol wrote:
Compare it to the quoted / illustrated text from the original Star Trek Concordance and you'll notice that the "Constitution Class" part has deliberately been added to make it appear official (I consider this to be fraudulent behaviour).
FYI, and apologies if you've heard this before, Greg Jein was a contributor to the original Concordance.