And finally, try to avoid using the terms "evolutionarily old" and "highly evolved".

OK, corrected, thanks. I definitely see the problem with 'highly evolved'. (For example, a "highly evolved" organism could lose and gain the ability to make a vitamin many times over). I was having trouble separating the ideas of 'older' (as in chronologically first) and 'autotroph' (as in independent). Animals don't dependably make the vitamins they need from plants because they can get these vitamins from plants. Plants, though, couldn't and can't depend upon something else producing them, so they make them on their own.

Much autotroph biomass is indigestible (think tree trunks) and some of the rest is deliberately poisonous.

Yes, of course. It was sloppy of me not to add the qualifier, 'if edible'. Instead, what about the validity of this statement: regardless of its edibility, and the amount and type of toxins that might be present, any plant part would be expected to have as many vitamins as a fruit part? The argument being that plants did not have evolutionary pressure to make their fruits particularly full of vitamins?

Furthermore, we ought to eat stuff that has good ingredients - we don't really care whether it makes them itself, or steals them from the manufacturer.

Agreed. My question is why the former would be healthier. Perhaps because manufacturers sequester more, in greater concentrations?