Why We Sleep: Unlocking the Power of Sleep and Dreams https://www.goodreads.com/book/show/34466963-why-we-sleep
There is no reason to discredit his claims as "false", unless you believe he made the false claim intentionally - which I don't believe he did.
He took complicated research and tried to simplify it and make it digestible to a general audience, and was successful at that.
I had a similar reaction when I first read the book, that some of his conclusions didn't make sense, but I've since backed off as I hear him speak, and believe he is one of the better researchers in the sleep space.
Of note, I work in the sleep space, and there is a TON of crap "science" out there, so I like to give support to those I believe are doing good work.
It's all very much groupthink, but that's sort of how pop scientific consensus works- with popular narratives and groups of datapoints and conclusions seemingly overthrowing other narratives and groups of datapoints and conclusions. The average layman is too busy to read either the book or the meticulous critique; I've only listened to about fifteen minutes of one of Walker's hour-long podcast interviews.
The takedown gets nitpicky certainly, but the first sections are very much targeting the main thesis of the book, which is that people are not getting enough sleep and that this lack of sleep is causing significant harm. Walker makes claims about the effect of sleep on lifespan and risk of disease that are completely unsupported, and in some cases even contradicted by the sources he provides.
You're right that it's groupthink, but it's also basic economy of attention. If the most basic of scrutiny of the opening chapter reveals sweeping unsupported claims, contradictions, and apparent outright fabrications I don't think it's unreasonable to disregard the author as a charlatan, if only because no one has infinite time to dig down to the foundations of every piece of pop-sci in the world.
I'm just pointing out that he made false claims. I'm not concerned with whether it was intentional - many of the claims he made in the book was false. Some of the premises he attempts to support were supported with conflicting information.
I simply wouldn't trust anything he's written in that book unless he republishes it with the corrected information, and retracts the mistakes. Has he done so?
The fact that he allows the book to continue to be publish and circulated is enough for me.
Also, he's been found citing his own books in his research papers - nothing shockingly wrong with that, but poor practice as far as research goes.
It would seem the Dimethyltryptamine is the last thing to be "topped up" in the brain then if what you say is true.