Personally, I doubt that (the emboldened section) is true. "Indicators" on helmets are very very rare. I think they would just serve to confuse, until or unless the driver was close enough to realise what they were. There might well be the danger of the effect where people are drawn towards something. There's a name for it but I forget what it is. If nothing else they sound like a distraction.
Personally, as somebody whose bike is completely compliant (I think), I get frustrated/annoyed at the extremely wide variance in bicycle lighting. Standards, that are actually enforced, would be a good thing. In the mean time we have people cycling around with all manner of lighting arrangements intended, at least in the riders' minds, to make them safer. In my city I've witnessed two variations of the same idiocy. Somebody with red lights on both the front and back of the bike, and somebody else with flashing white lights on both front and back.
PS, it would probably be the RVLR that would apply to the "indicators on a helmet" thing. Perhaps with a
reference to a BS. As we all know the police are very keen on checking that cyclists' lights display a BS kite mark. I bought an STZVO front light, as that apparently suffices for UK legislation. And more importantly has an upper cut-off, so I don't dazzle other road users. The RVLR are here, if you want to try to work out whether indicators on a helmet would be compliant -
https://www.legislation.gov.uk/uksi/1989/1796/contents. Have fun with that.