Kind of like git branch -d, which, as http://www.kernel.org/pub/software/scm/git/docs/git-branch.h... states, deletes the reflog as well? If it doesn't delete the reflog, then it git world, at least, it probably isn't considered to be fully destructive!
git branch -[dD] does not delete reflog entries for commits made to the branch.
A branch may have its own, separate reflog which would be deleted, but that is only a convenience feature as the man page you linked to documents WRT the -l option; the primary reflog still records all operations made on the branch.
You might find it useful to actually test stuff before posting links to man pages that you don't fully understand. I know I do. :P
