I’m ashamed I never noticed this until you pointed it out. Standards can be broken insidiously, and it’s disappointing that a company that cared about consistent UI enough to put out the HIG. Having typed that, I read the HIG on toggles and realized that those items in iOS aren’t checkboxes. A checkbox turns something on or off. The “round checkboxes” used in iOS are to select multiple items for further action. I don’t know what those are, or if/where they’re covered in the HIG.

https://developer.apple.com/design/human-interface-guideline...