I wasn't aware of this. That's unfortunate, because, despite some minor continuity errors (which she did acknowledge were there), the books give more depth to the overall story. The books are something I've been thinking about discussing in another thread, so I'm going to set one up at some point over the next few days.
The S.D. Perry books are officially an alternate universe known as "Perryverse" and along with the different universes of the various comic book series, the live action films and the mainstream (games canon) universes it forms the Resident Evil Multiverse.
Multiverse is a concept that has existed especially in comic books for decades. especially the DC Comics universe (Superman, Batman, Wonder Woman, Flash etc.) heavily explores the Multiverse concept. It basically means that there are various different universes, each with its own earth and therefore own versions of the characters living on earth. Each earth has it´s own canon and history. Some are similar to each other, while others are more different.
The TV series The Flash heavily explored the Multiverse in it´s recent Season with the villain Zoom hailing from Earth-2 and several villains being earth-2 versions of previously established characters. At the end of the season the superhero Jay Garrick was introduced who is the Flash on Earth-3 (in the TV version. In the comics Earth-3 is actually ruled by an evil Justice League, whose members are basically evil versions of the regular superheroes.)
Resident Evil has a Multiverse too (which is how I always viewed the games and movies anyway), where the three primary "Earths" being "Mainstream" (Games, CG movies, the RE stage play and the novel "Biohazard: Wicked North Sea"), "Anderson" (live action films) and "Perry" ( the S.D. Perry novels)
Other earths include the Wildtstorm comics, the Marvel vs Capcom games, the DeCandido novels or the non canon games like Operation Raccoon City.
A list of all the Universes in the RE Multiverse can be found here:
http://residentevil.wikia.com/wiki/Resident_Evil_Wiki:Multiverse
A reason why the Perry novels are their own universe is that there are some books in the series (Caliban Cove and Underworld) which are original stories that are not based on any of the games.