[jjk166]

> The question was "why is it needed".

No that was not the question. Why precisely sleep is essential is a complete non-sequitur to the original question, which was "does something occur during sleep which resembles what is described in TFA such that it can justifiably be called sleep."

As a general rule of thumb, if you find someone's responses incoherent, it's good practice to check what is actually being discussed.