Since the Rationale talks about Haskell Maybe, it should point to SRFI 189's Maybe as well.
While SRFI-202 does indeed mention Haskell's Maybe, it does so mainly to give an additional perspective on the "and-let*" form, which wasn't included at the time of writing SRFI-2 for whatever reason.
I have been using the extended "and-let*" form long before the first draft of SRFI-189, and even before I learned about Haskell's "do" notation. While I have nothing against including a pointer to SRFI-189 in the rationale for SRFI-202, I don't have any idea how to put it in words: SRFI-202 dwells solely on SRFI-2, extending it in the spirit of SRFI-201's "let*" form.
On the other hand, it probably also wouldn't hurt if a reference to SRFI-2 was included in the rationale for SRFI-189.