90% of his advice is pretty much just boilerplate self help stuff you can find in thousands of books on Amazon. That stuff gets you in the door and is meant to develop a sense of trust because you might see initial improvement and feel good from the advice.
It’s when he does the rug pull and starts introducing trad nonsense into it that determines how willing a person is to keep following through on listening to him.
Like you mentioned, this is an extremely common tactic used by religious leaders as well as cults. Back in the mid 20th century when the whole self help craze started, many cults took to framing themselves as self help groups to attract outsiders. NXIVM is probably the most infamous example of this. The first few meetings should seem like a normal support group but would soon start ramping up into full on cult mode.
Definitely don’t ever underestimate how quickly lack of sleep can mess you up mentally and physically.
Inflicting sleep deprivation on a person is widely recognized as a form of torture by human rights organizations as well as the UN.