It's likely that self-reporting is indeed an issue, but I wonder whether it's not a "balanced" issue on both sides. E.g. there are so many people who want to eat meat, they might be willing to lie about their health when asked how meat affects their health.
So maybe this is a myth perpetuated for burned meat, too??
Indeed. There's also the issue of lean meat vs. high-fat meat - where the body needs and benefits from the fat concentration being there as part of digestion and proper nutrients, along with another significant difference between white meat vs. red meat consumption.