Are 'True Horror Movies' actually true?

Before studying Horror movie's and not knowing much about it, I believed that if a horror movie claims it is true or even based on a true story, then that statement is correct.
However, this is not the case.

Whilst researching this concept, I came across this description which is shows that anyone can believe that a film is true, where in actual fact it is not.
I despise True Story Horror Movies that end up being 90% B.S. Or in the case of The Texas Chainsaw Massacre pretty much near 100% crap. Don'T get me wrong I like the Texas Chainsaw Massacre but saying it is based on a true story is like saying The Tooth Fairy is a real person or that the Easter Bunny is real  - http://www.horror-movies.ca/horror_15042.html


The False document technique
'By inventing and inserting documents that appear. The goal of a false document is to convince an audience that what is being presented is factual'

The Texas Chainsaw Massacre-The film opens with a voice-over and text suggesting that it is based on true event

If people are convinced the movie is based on real life events, they may be more likely to watch the film. It is also more realistic, compared to older films such as Frankenstein, where the villain is a monster.