o A note is included in the reference text that indicates that the
reference is to a target document of a lower maturity level, that
some caution should be used since it may be less stable than the
document from which it is being referenced, and, optionally,
explaining why the downref is appropriate.
There are many cases where cryptographic algorithms are specified in Informational RFC, and then a Standards-Track document is used to specify protocol conventions for using that algorithm. the algorithm specification is not unstable, and requiring a note like this sends the wrong message to the reader.