The University of Bath minimal HIIT protocol also used stationary bikes (3 20" intervals 3x/week).
Keep in mind that research in sports science is biased towards equipment like bikes because they make the study so much easier - safer to use, ensure consistent form, easier to get approval for the study and there's no need to coach the participants all that much.
Getting 20 inches on a stationary bike can be hard enough.
(couldn't resist. I actually didn't know " ("double prime") could mean seconds.)