I think you need to specify what kind of accessibility you mean.

I don't use iOS, but aren't the toggles red/green for off/on state, which could be problematic for colorblind people and that's why it requires the hints? Our control is white/blue.

I'm not sure if using 0/1 would be okay from the internationalization perspective, we might need to localize the numerals in languages that use different numeral systems (e.g. Eastern Arabic numerals). On the other hand, the 0/1 might be symbolic enough due to their use in the power symbol. But either way it's not clear that we need anything.

@RHo pointed out a concern when looking at the current MediaWiki theme layout that has a similar outcome to @Jdforrester-WMF question: the current off state could be seen misleading by users, resulting in confusion about what's on, what's off when facing the widget first-hand.
She also came up with some iterations, including trying "1" and "0" but we've concluded in a different approach brought up by her, that we (@RHo @Pginer-WMF and myself) are seeing advantageous over the current state:

Change 292888 had a related patch set uploaded (by VolkerE):
MediaWiki theme: Improve UX on ToggleSwitchWidget

https://gerrit.wikimedia.org/r/292888

I don't use iOS, but aren't the toggles red/green for off/on state ?

No, they are white vs green. The information you need to retrieve is communicated with color (a bad one for accessibility) and position (bad because of ltr rtl concerns).

which could be problematic for colorblind people and that's why it requires the hints?

It does not require the hints, the hints are provided to people who want them. Apple's philosophy here is that if something can be made better for certain disabilities, it is provided. This does not necessarily have to be color blindness. Interpreting position and color into a 'state' is a cognitive process that can be much more difficult for some people than for others. Interpreting a shape like I O, is often easier for them.

We don't 'need' them either I think. I've talked before about a Special:Accessibility preferences page where multiple of these changes could optionally be made. It might work as part of that.

@TheDJ Do you agree with the proposed change to clarify the off state?

Given that this task was hijacked to do something else, I've re-created my original task as T140812: ToggleSwitch: Consider adding 'on'/'1' and 'off'/'0' like in iOS accessibility.

Change 292888 merged by jenkins-bot:
MediaWiki theme: Improve UX on ToggleSwitchWidget

https://gerrit.wikimedia.org/r/292888