How do you know it's a lie if you haven't followed it? I don't understand why you care. If you don't believe, ok, you do not have to stay and read or post.
And one thing is always true with these threads. On those with some serious themes, there are always mumsnetters who have had similar experiences and give excellent advice. On those light-hearted CF threads, they bring a laugh to many and for some it might be the only cheerful thing they have had in the day. Laughing together creates a sense of belonging and is good for one's wellbeing. So what if an OP is not real? Why do you care? Why does it matter? The experiences of most replying are real, and that counts. The experiences of many lurkers hoping for advice in similar situations also matters, the advice that reaches those who genuinely are suffering is more important than deleting a thread started by a dubious OP.
I find it so annoying all this troll hunting, dubious posting, suspicious commenting clogging the threads... Just report and let MNHQ do their checks.
For what is worth, I personally think this one is true. But if it's not, I don't mind, it's been useful to hear advice about the topic, and I'm emotionally invested into knowing more and gives excitement to my day.