[racket] #lang/module equivalence

According to the docs,

      #lang s-exp module-path
      form ...

    is equivalent to

      (module name module-path
	form ...)

Yet:

  #lang s-exp lang/htdp-advanced

  (check-expect 1 2)

runs without error (though there is no error signaled either), whereas

  Welcome to DrRacket, version 5.0 [3m].
  Language: racket; memory limit: 128 MB.
  > (module M lang/htdp-advanced (check-expect 1 2))
  . check-expect: found a test that is not at the top level in:
(check-expect 1 2)

What am I missing?

Shriram