FWIW, people have glyph warping text (both on and off paths) using tools like Adobe Illustrator for as long as I can remember. I also don't quite get why one might want a capability that supports one type of glyph warping in the typeface itself.
I think this is really cool and interesting work by Nick Sherman. I just wonder if I'm correct about the limited applications, and what could be done to enable the kind of "contextual intelligence" that would enable fonts to better optimize themselves for a broader set of types of envelope deformations.