Documentation for `Version::LongVersion()` does not match implementation

The documentation for Version::LongVersion() describes it as returning a string of the form

ns-.[.patch][-rc][-closest-tag]-@[-dirty]-<build-profile>

Yet the implementation begins constructing said string with

std::ostringstream ostream;
ostream << VersionTag ();

In addition to the doc/implementation mismatch itself, it also leaves me a bit confused as to the intended use of the "version tag". Is it always expected to be an actual, official, tag from the main ns-3 repo? Or is it more free-form? Is it meant to be fed unaltered into the "long version"?