Google ads are based on the needs of web browser users. With the home page and category getting more traffic, it will be displayed first.
For posts, you need a minimum number of views to analyze google page as well as user behavior to display ads at the top of the article.
I don’t think it’s related to views, as we have articles with many thousands of views but ads are still not showing. The ad placeholder appears (white space), but no ad.
I have seen the occasional ad, but it’s very intermittent at best.
Google has the power to do whatever it wants in the placements you give it, including showing a blank rectangle. Not much the plugin can do to fight the Google brain.
One good idea is to first run your own house ads which you control. That way, you can see how the placements look and move them around, etc. because you are using your own “house” images for display ads to get everything working as you expect.
Then, when you are “all set”, and you are happy with your ad layout and that your house ads are running as expected, switch over to your network ad tags.
This is the standard way to go in the beginning. Test and get your own house ads (images) working as you expect, and they switch over to network tags.