Even if it’s compiling the entire compiler in 0.7 seconds it’s certainly not generating good code. Even then it’s dubious and likely skipping semantic checks, etc.
It's also worth noting that way back when, V could compile itself in almost 0.1s[0]. Now it's 7x slower. Of course, 0.1s -> 0.7s is very different than 10s -> 70s, but I think it is just another example of how programs start lightweight, but end up weighed down very, very quickly. What will V look like when all the promised features actually work?