I feel like Eventide was trying to help guitarists out regarding expression pedals and Aux. switches. The Ernie Ball 25K Jr. volume pedal is readily available if the guitarist does not already own one. Same goes for the Digitech Aux. switch.
So why the confusion? While Eventide wanted to simplify things, personally, I wanted rise to the occasion and learn a thing or two about expression pedals so I bought one and it didn’t work. (There is also the counterintuitive nature of using a volume pedal as an expression pedal rather than an expression pedal as an expression pedal which is slightly confusing.) In the end, I bought the stereo version of the Ernie Ball 25K Jr. There is nothing “Jr.” about it and I’m not sure they make it anymore, but it works. Moral of the tale is going with what the company recommends is usually the smart thing to do. An explanation from the company about why they recommend something (Ernie Ball 25k Jr.) is also helpful. Clear communication may not lead to understanding, but it will build trust, which is enough.