Obviously it's possible to write code that compiles while still not meeting requirements. My point is that the by leveraging the type system he was able to offload a lot of those checks to compile time rather than runtime.

It's not impossible, but it's harder in Scala. Actually the closest comparison I could make would be Python, where I had a similar experience - as soon as my code stopped producing errors, it was doing what I wanted it to (the difference being that the errors were at runtime rather than compile time). Whereas in Java and C and even ML I've written programs that compiled correctly but did something very different from what they were meant to.