You've got to remember a few contextual things about this:
1) The members of the Dead have done an astounding amount of drugs, over several decades.
2) Phil obviously loves having more knobs than any reasonable person would ever want, for his own whimsical reasons that have nothing to do with logic, science, or practicality.
3) He has had roadies for his entire career, so the concept of getting the most efficient functionality out of his rig has probably not crossed his mind even once.
There is absolutely no sense or logic to using that Meyer unit "in opposition to" the Enhance and EQ of the Eden pre, except in Phil's mind, and I guess for somebody in a Dead cover band who has to look 100% authentic.