I’m less concerned about this as there are various solutions (including simply rewriting the specification text for any adopted procedures/syntax/etc.) we can adopt.
Actually that doesn't work either, because you can't prepare a clean-room *specification* unless you have a specification for the specification, which pretty much is a specification. So your supposedly clean specification ends up being a derivative work of the original specification.
It's annoying that the Scheme specifications are not (recognized as) libre, but there are worse things: gcc is libre software, but the various C specifications are neither libre nor even available gratis.