It's pretty common when it comes to oils. You get a snap shot of one condition ..and you assign it to the oil brand. You have to ignore millions that used the product and didn't experience the same condition.
Suppose the engine in question was a known sludge engine from Toyota? He's one of the NEVER AGAIN!!!! types. The "never again" isn't necessarily a bad thing ..as long as there's plenty of whatever it is you're finding problem with. Otherwise, you quickly run out of options.
My evolutions on some products is so protracted that I find total dissatisfaction with the new product in terms of either performance or quality ($ value). I then deem it junk. I then go to an alternative item and also find that it's junk ..and that junk is the new standard for quality.
I love how narrow minded some people are and how they think that a company as huge as Pennzoil (or SOPUS) would actually market a product that would do harm to your engine.
Do you think they would be around all these years if the rumors were true?

I laugh and say let them be taxed for the idiots they are.