I think Fishkin’s taxonomy is helpful in understanding the UIs mentioned in the paper, in terms of embodiment and metaphor. However, there are a lot of other types of UIs left out of the taxonomy that Fishkin’s taxonomy could not be very helpful to help people understand.
For example, his taxonomy on the embodiment axis didn’t discuss the distance between human body and the input device at all. TUI doesn’t need to be literally using hands to do input. For example, we could have Siri or Echo as part of the TUI input system.
Another issue about Fishkin’s taxonomy is his metaphor axis, which only considers the shape and the motion. I think the metaphor concept could be pushed much further. For example, the taxonomy on the metaphor axis could also include all the other human senses other than sight, such as taste, touch, smell, and sound.
Moreover, I would suggest the metaphor axis could also include personality, for people to understand more robot-type TUI systems, such as Baymax in the movie of Big Hero 6.