I if ever meet the Apple devs responsible for iOS accessibility keyboard control I‘ll go to jail for a long time. Keypresses for tab, shift+tab and arrow keys do not even reach the browser, the OS catches them and moves focus to whatever it sees fit to be the next focusable item. Tabindex and roles are also just recommendations and no surefire way of controlling focusability.
Whatever those people take I hope it‘s laced with fent.