Sleep-like states exist in animals with nervous systems with a complexity above that found in flatworms, even snails sleep. Sleep therefore appears to be an essential characteristic of more complex biological nervous systems, i.e. biological computers, should you care to stretch the analogy. The more complex the nervous system, the greater the requirement for sleep.

What is described in the OP is therefore not a specific characteristic of sleep. It may however be a "useful" rhetorical device.

I do however object to the extensive use of such rhetorical tricks in the conversations that surround LLMs. For example, why does a consumer-grade LLM display "thinking" while it is actually sending data from my computer to some datacentre, processing it, and sending the result back? Equally, why does it output human-emotive phrases such as "sorry" when such computation is revealed to be incorrect?

Such rhetorical tricks, and more, likely underlie to a large degree the popularity of LLMs, despite their actual performance being clearly below what the rhetoric implies.

> I don't think it's necessarily correct to think of sleep in terms of "it is necessary for animals or they will die". It might be more useful to think of it as "it was so useful that animals who slept outcompeted all the animals who didn't".

You're talking about different things: biological necessity and evolutionary benefit.

You can find out about the former by preventing an animal from sleeping (but otherwise provide all other needed things), and seeing if it will eventually die.