Bella, side hopping to your opposite of your forward foot allows you to get higher as it gives you more clearance. I am right foot forward, if I side hop to my right I will eventually get to height that i will struggle with, not because it is too high, but because my foot catches the obstacle on my way up. This happens, because your forward foot is your stronger foot/leg so naturally when on the back wheel you foot and leg is pulling the bike in the same direction as your forward foot.
By side hopping to your back foot side (weaker foot/leg), you are having to put that effort in to get the bike to go that way. This allows you to have more clearance, go higher and control your movement during your side hop.