Toggle buttons are supposed to have an instant effect. It's an anti pattern to gate the effect on a submit.

According to who? It's a restyled checkbox.

Well, stuff like this used to be encoded in HIGs (Human Interface Guidelines). The GNOME HIG, back in the day, had the parent's recommendation, as well as the rationale for it: so that the feedback is immediate, and the user can then visually see the effect that that option has.

Gating it on a submit forces a user who is looking for something & not finding it into a "try one thing, submit, evaluate, open settings, undo that, try different thing, submit…" loop, which is a lot longer.