On the contrary, that is exactly what they are for.  See <https://srfi.schemers.org/about.html>:  "We write concrete, detailed proposals and sample implementations for libraries and other additions to the Scheme language, and we encourage Scheme implementors to adopt them."  A proposal is a suggestion, not a specification.

The total discussion period must not exceed 90 days. Active discussion or revision after 90 days normally suggests that a proposal has been revised at least 3 times and is not yet mature enough for standardization [emphasis added by Arthur]. At the end of the 60-90 day comment period, the authors can choose to withdraw the proposal. If the editors determine that insufficient time for discussion has followed a significant revision of the proposal, the proposal will be withdrawn.