Paramount considers it canon.
No, they don't.
At the time of its publication, then-Paramount Licensing and later Viacom Licensing (now CBS Consumer Products), were telling the editors of the Star Trek tie-in books, novels and RPGs to consider the dates in the Chronology as canonical for them
, to start keeping things consistent. But the writers for the varis ST TV series and movies
constrained by the Chronology and can (and did) make many changes to the Okudas' "conjectures".
It's a great book, but not a definitive text IMO.
It was never intended to be. Neither was the Goldsteins' version.