No, not true. I can see a million ways that doesn't work - most claims of this are a trick, and the letters are arranged so that the reader can still see certain syllable arrangements. It also doesn't work so well for nonsensical sentences where the reader can't grasp the sense and general meaning of words to make an educated guess. Your test isn't very scientific.
Also, "so it is true onley the first and the last letter need to be in the correct place" is a stupid statement in itself. Doesn't really work for words like fart and frat, does it?