Font hinting lets you move points around based on sizes, dpi and rendering modes using a stack-based bytecode language.

Sure the primary use case for many years was to cope with low-resolution but it can be used in the way the poster above described. In fact you can use it in the other direction too so that larger sizes take on more specific characteristics instead of having two fonts and a hack that switches at 20pt like they're doing with San Francisco.

Source: Have actually TrueType hinted fonts.