and you know this how?
yogis,saints,mystics,true philosophers all know this is false, the true self is eternal,never born, deathless, perfect, you will not come to this self knowledge in this life but sometime you will and you will be free at last.
You cannot make a general statement like that. Also, what is a "true" philosopher? Does a "true" philosopher hold a certain degree? Do "true" philosophers write X amount of books? Explain what a "true" philosopher is.
Second, there are many philosophers (I would consider them "true" philosophers"), such as Daniel Dennet, Sam Harris, Bertrand Russel, Friedrich Nietzche, and Jean Paul Sartre, who, I would surmise, do not believe there is an eternal self or consciousness after we die.
Third, most yogis, saints, and mystics are a bunch of charlatans.