In my optionion the fallback is not useful, and that's why I have filed the linked redmine ticket two years ago ;-). Nevertheless it is possible that someone who is using the current facter version has asked himself "How can I determine if the current agent runs Solaris 11?" and has answered this question with "looks like operatingsystemrelease gives me what I want, so let's write `if $::operatingsystemrelease == '5.11' { }" This will fail of course if we change the fact now.