That is the one part about typography that has always confused me - San Francisco is clearly a variation of FF DIN. Can you buy a 'licenses' to use and make your own variation of a typeface?
https://en.wikipedia.org/wiki/Adobe_Systems,_Inc._v._Souther....
https://en.wikipedia.org/wiki/Intellectual_property_protecti...
There's a similar situation with clothing, IIRC, which explains the prevalence of brand logos.
IANAL, obviously.
Most fonts though (TrueType and OpenType) have a hinting language in them which is code and it is copyrightable since it is computer software. This means you can't just copy DIN font files themselves and distribute them freely without permission.
You can however take the outlines from the font, recreate the hints manually and then distribute it.
That said, there are such things as design patents and of course, trademarks. Design patents aren't used too much, but do protect the design itself. Trademarks of course allow you to protect the name.
Would Apple have paid to modify and use FF DIN in their devices?