Below is a video displaying the concepts talked about in your lesson.
Firstly, pay attention to how my thumb is muting the lower (heavier) strings by resting or laying on them.
Secondly, notice how my pick DOES NOT stop moving AT ALL, even between the high e (1st) and B (2nd) string. Your pick should never fully stop moving when using this technique. Poor playing habits can develop and hurt your progress if you are not careful about this concept.
D major Arpeggio
Here is a video of the Amin arpeggio at different speeds. Again, my thumb is resting against the strings I am NOT playing, and my pick is gliding over the strings in a smooth, controlled motion.
A minor Arpeggio
Below is a video of how NOT to sweep pick. Notice how some of the notes ring together when they should be played separately, one after the other. Also notice the jerky, inconsistent motion that my picking hand makes when I should be making the smooth, sweeping motion. This results in uneven pick attacks (some notes are louder and some are quieter than others), sloppy excess string noise, bad timing, early fatigue when playing for an extended amount of time (such as playing a full set in front of an audience or even one song), and a mess of other habits and problems that will limit your growth and progress. Simply being aware of how NOT to sweep pick will drastically increase the results you get from your own practice.