RBS, Ruby’s new type signature language

Can someone explain why the types cannot live in Ruby code itself (after an appropriate version bump)?

Python 3 incorporated types into the language itself, in a similar way (though non-reified) to PHP. This seems much easier to deal with than requiring two files (.rb and .rbs) to describe a single data structure.

I can well imagine that it might be because ruby's formal syntax is already utterly bonkers, and the thought of adding types to it in any usable fashion gave someone a seizure.

Haven't used ruby in years for the typical reasons people move away from it (performance, strong types, GVL, etc.) but syntax is #1 reason I like programming in Ruby. I did mostly ruby for about 5 years and really grew to love it! It may seem bonkers at first but quite enjoyable once you understand it. Now nearly 4 years later of mostly javascript, golang, python, haskell I still regularly stop and think to my self how much I miss ruby!