I really don't like Jai's presentation because there is essentially no text material is available and thus much harder to discuss anything. For the posteriority the actual demonstration is available here [1]; it shows that it is a multi-staged compilation model like Zig, which is very useful and also quite limited.
[1] https://youtu.be/iVN3LLf4wMg?t=1903 (or, seek to 31:43)