Apple seems to be switching up its preferred font weights. There is a renewed tendency by Apple design towards heavier weights overall. The iPhone 7 packaging uses a heavier weight for the box branding. iOS 10 uses heavy fonts too with the News, Home and Music apps. The keynote slides used a lot of bold San Francisco too. It’s not all San Francisco though, Myriad is still used on the new product pages.
I like the move back towards thicker fonts. The super-thin font trend brought about by iOS 7 is annoying. When everything is thin, the impact is lost. There are also readability issues (which even Apple has to specially workaround sometimes with using thin fonts for everything and limits the backgrounds the text can be superimposed on.
All text faces need to be used in moderation. Everything bold or everything light is not a good balance. Bold faces are good for titles and logos. Use them.