The real problem with these guides is that they always assume the hiring manager is 100% adversarial and will be using everything in their power to minimize your salary.
Some companies definitely operate that way, but as a hiring manager I have a lot of incentives to hire and retain good employees. If I'm constantly low-balling every candidate and squeezing the lowest possible salary out of them, I'm also going to be constantly losing my best people when they realize they're underpaid in 6 months. Then I have to go out and recruit, hire, and re-train someone else.
It depends on the company, of course, but many hiring managers are more than happy to carve out as much compensation as they can get away with for new hires. It improves team morale, decreases team turnover, and gives the hiring manager additional leverage over highly paid employees who know they can't just walk out the door into a higher salary somewhere else.
Unfortunately, most candidates these days have been taught (by guides like this and other internet wisdom) that salary negotiation must be played like an ultra-competitive game where the first move is to always force the company to name their price first. Hiring managers aren't dumb and we do this all the time, so whenever a candidate starts reciting hardball negotiation playbooks I just start with an offer that's 5-10% lower than what I think we'll end up with. The candidate then comes back and demands something 5-10% higher and we settle back at the number I had in mind anyway.
In the odd event that the candidate doesn't negotiate back up after forcing me to go first, I just throw the extra money into the offer anyway. Employees are even happier to see that I've come up on my initial offer, which is a great way to start the relationship.
On the other hand, when some candidates come in demanding multiple months of delays while they collect competing offers and want to go through endless rounds of re-negotiation even after we've agreed on a number, I just cut them loose and wish them luck on their career search. Unless you're a FAANG hiring many people at once, it doesn't make sense to play endless games with candidates who are going to end up at a FAANG anyway.