Why isn't "Flash on Silent" working like you expected if you're using "LED Flash for Alerts" in the iPhone's Accessibility settings?

It's because you're coming at it backwards.

What iOS Flash on Silent really means

It's not "Flash on Silent [only]", which is useful for dopes that can hear.

It's "Flash on Silent [even though your switch is telling your phone to be quiet]"!

Make sense?

If you're deaf, the flash is the sound.

If you have your ringer switched to silent, there shouldn't be a flash. The sound is off.

If you set "Flash on Silent", your iPhone will "ring" even though it's supposed to be quiet.

That is to say, "Flash on Silent" is equivalent to a setting that'd say "Ring on Silent".

It also appears that setting "LED Flash for Alerts" off overrides the ability to flash on silent. That's too bad for hearing folk, where the flash only on silent would be awesome. You must have LED Flash for Alerts on for the Flash on Silent to have any effect (afaict).

I hope that makes more sense. Don't worry, everyone got this wrong coming at it from the land of the hearing enabled.