The GP does not appear to have any misconceptions.
From your first link, "how relevant your ad text is to searches, how likely people are to click your ad, and the quality of their experience once they reach your landing page"
This is all data that's generated based on the overall learning that Adwords does against your site presence. It's why it takes weeks to really get your data settled in, and why if you (or your Google rep) start to mismanage your account, things will rapidly go bad.
The GP story was based on the premise that opting a campaign into the display network increased CPC on search ad clicks. I know for a fact that it is not possible.
I am not at liberty to go through each issue the GP had, so I linked to the best source of truth on this subject.
The effect of lowered account-wide CTR on CPC is something that has been experienced by a lot of people who have run Adwords campaigns. I saw it discussed a lot on forums about affiliate marketing. They always said, whatever you do, avoid the "account slap" that comes if your CTR plummets. I saw it myself on more than one account.
Maybe it isn't causal? But the correlation is pretty near 100%.
From your first link, "how relevant your ad text is to searches, how likely people are to click your ad, and the quality of their experience once they reach your landing page"
This is all data that's generated based on the overall learning that Adwords does against your site presence. It's why it takes weeks to really get your data settled in, and why if you (or your Google rep) start to mismanage your account, things will rapidly go bad.