I thought it interesting that both Constitution and Enterprise are used here as the class type of our favorite starship in the same paragraph. What's THAT all about?
Must be the "Question Mark IX/01 Starship Class".
That paragraph is obviously written from a weird in-universe point of view.
Today, we know from Matt Jefferies that the extra "C" was derived from the third "C" in Soviet designations, so the "esthetic balance" has a rather interesting ring to it.
So apparently the Enterprise
and her sister ships (the only TOS vessels seen with an "NCC" registry) belong to the "Enterprise Class" (correct) - but are "Constitution-type" space cruisers?!?
So Bjo Trimble considered [then] undisputed information from The Making of Star Trek
but discarded it later on behalf of Constitution Class exclusively.