>>3
Racket, the language, does not claim to be a Scheme, but a descendant of it:
Depending on how you look at it, Racket is a programming language—a dialect of Lisp and a descendant of Scheme; ...
(From https://docs.racket-lang.org/guide/intro.html )
Racket, the system, has a R6RS language that is a Scheme, and it mostly conforms to the standard, with some exceptions that don't look that drastic to me:
https://docs.racket-lang.org/r6rs/r6rs-mod.html
https://docs.racket-lang.org/r6rs/conformance.html
>>5
I was aware of the standard conforming #lang, and even that it's no longer considered (PLT)Scheme. Early on they adopted a well meaning policy of ``embrace and exteninguish'' which is universal among Scheme implementations to varying degrees.