MsHuggys, well said and well explained. what you said is the consensus most of us go by over what we learned over the years.
G* is probably putting its own interest first, saying to advertisers, it's likely many people won't click your ads if deep within or at the end of content, why don't you be there where everyone will see, if there are no clicks at least you were guaranteed a pageview, you paid for branding which comes free or next to nothing (not good for adsense publishers though).
Experiment starts at home (here), I read your entire post twice, because I liked what you said, but I usually skip most long posts and go directly to the phrase related to what I was looking for.
In my case, I would've clicked an ad if it was at the end, I was determined to read the whole post, it was what I wanted, but it won't have been what I wanted most times and likely to have either clicked an ad at the top or clicked the back button.
Thanks for taking the time to write this long post.