On the other hand, we have the opposite relationship with fruits. When our ancestors ate fruits, they played a pivotal role in facilitating the plant's reproductive fitness by dispersing the seeds, at times with the excellent complimentary fertilizer that is human excrement. In this case, the plant has an evolutionary incentive to produce more nutritious fruits to encourage such human consumption.
There are a lot of "vegetables" that are actually botanical fruits such cucumbers, zucchini, tomato, etc. (note they all contain seeds). They are much better alternatives than true vegetables (spinach/kale) for juicing if you are trying to avoid sugar or somehow don't like sweet juice.
It also doesn't sound right to me to refer to liquified vegetables as "juice", when I've long thought the term refers to the liquid produced from squeezing a fruit (not to mention liquified spinach/kale sounds a bit nasty)
When it comes to research publications in general, I very much prefer to hear an objective, good faith presentation of the major viewpoints, with the author taking an opinionated but measured take in the conclusion as they review the overall weight of the literature. I'm sure there are issues with this "triune brain" model, but at a certain level every model is inaccurate; the real question is whether a model is useful in its framework, and the answer has a degree of subjectivity such that I do not think it is fair to categorically reject the perspectives of opposing experts in the field.