But then this recommendation becomes vacuous. No one is recommending learning math by deriving everything yourself.
Exactly. What’s really being referred to? Lower cost and more scheduling flexibility perhaps?
Maybe, but I think people do mean a literal human, and I do think books were always available, and if that alone were the key... then I hesitatingly make the simple argument that it would've already been done. One might make a similar argument about why Khan Academy isn't a blowout success in the US.