I think you’re missing the bigger point – since the zippering is to do with how the expression pedal is being sampled it’s actually there for everything, it’s just particularly noticeable when using it to control volume. It’s also there if you use it as a wah, or to control any parameters.
The expression pedal is basically useless.
I wasn’t expecting a multi-fx pedal, I knew exactly what I getting. I was shocked that a pedal with that much DSP grunt would have trouble doing the simplest possible signal processing algorithm, and further shocked when an Eventide representative said basically “yeah, we made a bad design choice but we’re not going to fix it”, and then didn’t bother to answer my question “in what scenario would this behaviour in an expression pedal be actually OK?”
I got a Line6 HX Stomp, which is way more flexible, has way more features, doesn’t charge you per effect, and the expression pedal works perfectly. And has linear and log scaling. Yes, there a few sounds that the H9 does better, but they happen to be ones I would rarely use, and the HX Stomp equivalents are perfectly useable.