Taking effect instantly is not really indicated by the control shape; it's indicated by whether or not the form has a button equivalent to "apply". Settings pages with checkboxes that applied immediately have been common for years; this distinction is not nearly as clear cut as you make out. I suspect what is going on is that both toggle switches and the removal of a separate apply step has gone on gradually at the same time.
But a good thing to think about is all the other controls: drop downs, text entry boxes, date pickers - these have no second version which might apply instantly or not! So it's a mistake to think that information is conveyed by the look of the control.