Implementations are permitted to ignore user-specified hash functions in certain circumstances. Specifically, if the equality predicate, whether passed as part of a comparator or explicitly, is more fine-grained (in the sense of R7RS-small section 6.1) thanequal?, the implementation is free — indeed, is encouraged — to ignore the user-specified hash function and use something implementation-dependent.
Without your first paragraph, this post-finalization note on its own seems more broad than I imagine that you intended. Don't you just want to relax the restriction on make-eq-comparator and make-eqv-comparator?