Yes, those are G20s! I saw it on someone’s post on Reddit and they are much more comfortable on the sides of the thumbs than the DSA keycaps.
Rotary encoder is set for mouse wheel scroll by default, which has the advantage of smoothly scrolling and being usable everywhere (Kakoune, tmux etc.) as opposed to arrow keys or PgUp/Down. (Granted, after I got the trackball the mouse is easier to reach than before, so this is less useful.) The downside is that the mouse cursor has to be on the window to scroll. It’s used for volume control, horizontal scroll and tmux window switching on other layers, but those only get occasional use.