UnicodeCowan has not yet fully been incorporated in the draft, in particular point 15:
- All Scheme implementations shall permit the sequence \x<hexdigits>; to appear in Scheme symbols (and therefore identifiers). If the character with the given Unicode scalar value is supported by the implementation, symbols containing such a sequence are equivalent to symbols containing the corresponding character. The symbol->string procedure may return the actual character or the escape sequence at the implementation's option, but any leading zeros must be removed from the escape sequence.
Actually it has been; see 7.1.1. But it needs to come out, because it's broken.