Whether or not something is "moderate" or "vigorous" all depends on how fit you are and how hard you push yourself. There's no solid definition of what it means but in general the intensities are defined like:
Light - Easy. Could do this for hours. Examples: A walk around the park.
Moderate - A struggle, but nothing you can't handle. Examples: Bike riding around the neighborhood with some hills. Beginners dance lessons.
Vigorous - Hard. Can't be sustained for long. Your breathing is hard and your heartbeat is fast. Examples: Sprinting. Swimming laps in a pool as fast as you can. Bike racing.
A way to determine your intensity is by singing a verse of a song. If you struggle to even finish the verse without taking a breath, then you are in vigorous. If you can complete the verse but you have trouble keeping the tune, then you're in moderate. If you can finish the verse without issues, then you are in light intensity.
So for the mini stepper, if you really pushed hard you probably could get to the "vigorous" range, but I'd imagine it would be very difficult to use the bands effectively. It most likely will bring you to the "light" to "moderate" range as most.