One of the authors here. We didnt want to change the AST in a way that would be backwards incompatible with vanilla PHP. There is some luxury in being able to turn off this extension when needed. We also have a large enough existing codebase that switching to SPL types everywhere was a non-starter. Our goal here was partly to be able to use PHP's native types and still get some good coverage.
Phpdoc may not seem ideal, and it's not, but it has afforded some significant flexibility
Phpdoc may not seem ideal, and it's not, but it has afforded some significant flexibility