I have to assume the genius was off script. The shop I worked at had people sign a document before authorizing anything destructive. We usually imaged the disk anyway.
Definitely agree with the larger point though. PCs (phones, tablets, etc) are ridiculously hard to use and unreliable even if you kinda sorta know what you're doing.
I worked at the Apple 5th avenue retail store until April, and there is a document that has to be signed acknowledging that you could lose all your data. That said, it's usually framed as a "this probably won't happen, but just in case"
Back before Best Buy had the "Geeksquad", we had the exact same type of form. And we framed it the same way, actually had to almost underplay that bad things could happen.
Definitely agree with the larger point though. PCs (phones, tablets, etc) are ridiculously hard to use and unreliable even if you kinda sorta know what you're doing.