This is rather overstating the shortcomings for small sizes – Apple only uses SF Compact on the Watch; SF Text is used on even the smallest elements in iOS and

This is rather overstating the shortcomings for small sizes – Apple only uses SF Compact on the Watch; SF Text is used on even the smallest elements in iOS and macOS. Inter reduces approximately as well. As for tracking, it’s already a good practice to use a slightly higher `letter-spacing` value at small sizes (something UIkit does automatically), so this isn’t really a function of the font family.