Hi John,
Glad you are enjoying the course!
My recommendation of playing downbeats with downstrokes and upbeats with upstrokes, is for beginning sightreaders who have a hard time keeping track of where they are on the beat. The initial advice is to try to keep track of them with your foot. However, some players have a hard time synchronizing their foot to what they’re playing in the beginning, so the alternative is to use the alternate strokes of the pick as a guide. This seems to solve the issue for many. Once it becomes second nature, it is easier to get the foot going instead. At that point you can use whatever stroke is convenient anywhere, which is what we all should eventually be doing. So once again, its only a last resort strategy to help you develop an awareness of where you are in the measure when learning how to read rhythms.