Ramsey is saying 8% for 1 of 2 reasons.
1. He either wants to distinguish himself from the 4% Rule (hopefully based on some kind of info)
2. It's a play on his "stock market goes up 10%+ a year" guidance
About 10 years ago, I remember Ramsey was going through a series of confrontations with people who disagreed with him online. He'd always lead with "what are you studying in school?" and "have you ever worked in business?", and maybe "do you own your own home?"
It was almost always a 20-yo liberal arts major living at home, and Ramsey would "win" the argument. Except one time a kid got Ramsey to admit something about the market ROR, but explained it in some weird way. The kid said, "so why don't you just say that it's [whatever percent]?" and Ramsey flipped his lid with because it's called the Dave Ramsey show, and I'll say what I want.
Following that, Ramsey said the one the kid said.
I was following those closely because I was a Feature Writer and Section Editor for a couple websites, and one of them had my bio as being that I was a "consumer advocate." Ramsey said multiple times on the radio - never naming me, so maybe not referring to me - about how there are some people online calling themselves consumer advocates, but they haven't been helping people for 30 years.