I think it’s probably more of a creative limitation than specifically a processor limitation. I’ve said it before but I see Elektron gear—particularly this and the Octatrack—as an extended hardware version of the oldskool sample trackers of the 90s. If you want polyphony, use sample/parameter locks on a track that isn’t playing anything where you want the polyphony to appear.
Or perhaps with each track having its own filter and distortion, both of pretty decent quality, it increases processing power enough that it can only really handle 8 monophonic channels…?