The Evolution of RSS
Dave Winer: I was surprised that the top-level element in the RDF branch is not <rss> -- it's <rdf:rdf>. According to The Evolution of RSS, apparently 0.9 and 1.0 use <rdf:rdf> whereas 0.91 and 0.92 use <rss>.
And then later: Why is RSS 1.0 called RSS? According to the RSS 1.0 spec, RSS is an acronym for RDF Site Summary. This is consistent with what the waybackMachine captured for RSS 0.9. The RSS 0.91 spec claims that RSS is not an acronym.
I am not a stakeholder in this naming issue, nor can I claim based on personal experience that any of the above references are authoritative, but based on these references alone, it seems to me that one could ask the converse to both of these questions: i.e, why is RSS 0.91 called RSS, and why did the RSS 0.91 branch use <rss> instead of <rdf:rdf>?