I actually get where the author's coming from. While it's tempting to think of Racket as a Scheme implementation, and that was at one time true, the situation

I actually get where the author's coming from. While it's tempting to think of Racket as a Scheme implementation, and that was at one time true, the situation these days is quite different. It's a lot more accurate to say that Racket ships with a Scheme-like default language (and an actual R5RS-compatible Scheme), but that it's actually a wonderful language toolkit. Racket has the ability for individual modules to use their own syntax. Not macros; full-fledged syntax. Racket ships with several Lisp-like syntaxes, but it also ships with Datalog and ALGOL-68. And this is very much unique to Racket.