I believe that Howards was brought in when we had some "why is it like this?" questions. I don't know the details in this specific case.
To start, I haven't figured out what I can say publicly about the process and what we have to keep to ourselves. So, unfortunately, I can't get too into the details yet. However, someone earlier commented about component modeling vs. the HX "sub circuit" modeling.
In HX, we have DSP elements that can change the sound; filters, gain, tube simulators, power supply sag, etc. All of these start at a neutral point, like the DSP is zeroed out. When making HX models, we measure the change of sound in a small bit of analog circuit, and then we set the DSP elements to make those same changes. All of the sonic changes have to be matched manually or semi-manually. Anything that is "feel" related comes along with matching the measurements. If it's not quite there, we can tune it manually. It's a long process, but everyone liked the results. In addition, this type of modeling easily allows original models to be made.
Agoura modeling is different. Like I said, I can't get into it, but it doesn't start with DSP set at a zero point that we then manually configure.
I know this might still leave you in the dark. As an egalitarian, DIY punk rocker, I want to share everything and live in an open source world. I'd love to talk about the fine details in depth. It's so new, so specific, and took a lot of R&D to develop. I'm sure we will have talking points and informational video in the mid-length future. Right now, we're all working on 1.2, 1.3, and beyond.
Thanks!
Ben