I believe that buster's original observation was very insightful. I have been away from BITOG for a couple of years (with only a quick peek at topics from time-to-time) and the marketing emphasis has changed from the large Multi-Nationals. I see a dual emphasis ...
1 - (per Buster) Engine cleanliness and anti-sludge claims (possibly driven by some of the sludge problems of the Lexus and Toyota engines??)
2 - Extended drain guarantess (M1EP, Castrol Edge and now PZ Ultra). Probably driven by the GM OLM and the Honda Maintenance Minder. [My wife's new Traverse was giving her an OCI of 13K on dino. It is now full of Castrol Edge....but i digress]
If you assume that the auto market in the U.S. is mature....one way for big oil companies to make more $$$ is to fill every possible niche within the market (dino, semi-synthetic, HM, synthetic, extended drain synthetics, etc.). Each has their own target market, price points and value.
I personally tend to gravitate toward a good dino or the top-end extended drain oil. Everything else in the middle is just too confusing with too much overlap.
Good observation Buster!!!