I agree - this topic fascinating and I would like to know more. Advertising and its associated data gathering has profound effects on podcasting. I suppose there is a positive effect in that podcasting is financially supported, but there are many negative effects including massive user privacy violation, user annoyance and market distortions. When I search for a podcast on a particular topic the result is usually from whoever paid the most money instead of what I am actually searching for.
Readers of this thread might find this old MPU Talk forum thread (link below) of interest. This is from 2019; the podcast industry has changed substantially since then. The 5th paragraph in the first post (beginning with “But that could change …”) may have been prophetic.
link: https://talk.macpowerusers.com/t/growth-of-the-podcast-industry-analytics-and-rad/10295?u=arthur
Apple’s tightening of its podcast download reporting is probably a step in the right direction for more accurate analytics reporting without necessarily compromising user privacy.