Comment by magicalhippo

From what I can gather, the underlying feature that enables this is vontextual alternates[1], primarily intended to adjust letters based on adjacent letters to improve legibility.

edit: I see the referenced inspiration[2] explains it in detail.

[1]: https://typenetwork.com/articles/opentype-at-work-contextual...

[2]: https://blog.glyphdrawing.club/font-with-built-in-syntax-hig...