The book these came from originally is a core book, the sword coast adventurer's guide, and then they were reprinted in the most recent book, Tasha'a cauldron of everything, also a core book. The question of what is and isn't "core" is a little blurry (re: ALL the planeshift content, technically official). You can use the adventure's league as a kind of guide, they have some restricting rules on what is and isn't allowed, but I personally dislike using AL as a touchstone for home games or third party made games.
But the question really should be: how many books OTHER than the basic player's handbook are they planning on looking at? We already have tief subraces from mordykordy, is that book next? How far will it go, considering people have issues with class power creep in the subsequent books? No one who has ever played a gish or hybrid class can deny that these spells are needed.