Historically, the community consensus has broadly (but by no means universally) been that all the FS2 ships and technologies did already exist in the Shivan arsenal, but for whatever reason, they didn't deploy them during FS1. Basically, this is because of the interpretation of the FS1 ancient monologues being about a fleet based around a Lucifer, or something very similar ("In subspace they cannot use their shield"), and if this is the case, then the Shivans advanced almost not at all in 8000 years - it would be inconsistent for them to suddenly jump so far ahead in just a few decades after such a long idle period.
There have been any number of potential reasons for this put forward in campaigns and on the forums, including possible explanations that accept the tech jump, but there's never been anything even close to generally accepted. The only thing we have that's even vaguely close to canon is a vague description on the FS2 box of the original Shivan force as a scouting fleet, but this is highly ambiguous (could be interpreted as slightly tongue in cheek, designed to imply the overwhelming superiority of the new FS2 fleet vs. the FS1 fleet, rendering it no more significant than a scouting fleet) , and worse yet, was probably written by Interplay, not Volition.
TL;DR: The classes in question very possibly did exist, but there's no canon answer either way.