
YuriP |

This is probably wrong but the necromancer's Quickened Casting feat is without the frequency entry but once that its description text is different from classic feat (it says "If your next action is to cast a necromancer cantrip or a necromancer spell" (even with same feat name) with luck this may be a different feat that allows to reduces the action of some spells without the once per minute restriction.

Squiggit |

It's almost certainly just an editing error. Even being limited to just necromancer spells, -1 action to all your spellcasting is incredibly strong.
That said it is a little weird that the frequency got dropped and the class restriction got added when otherwise the feat text looks like a copy/paste. So maybe it is meant to do something slightly different, just probably not this.