No. Of course it isn't, but mods often don't see every off topic post. You can report them if you feel they are and they will be evaluated and each circumstance will be taken on a case by case basis. Sometimes a post is reported that is off topic and a mod will only delete that one even though there's several other responses to it. Those are all also clearly off topic but they either might not have looked for more or not spotted them. Sometimes there's pages of off topic responses and sometimes you can miss them. If you feel like one post has been removed and others haven't then either report them or bring the issue up in Meta.