First, jumping with both legs isn't "improper", it's just not ollying. There are situations where popping is the proper thing to do.
Second, can you ollie better when you're not moving? I personally find it easier to ollie when I'm not moving, becuase when I'm moving I'm hesitant about throwing my weight onto my back leg. If so, that's just practice.
Yeah, that's me, Tracer Bullet. I've got eight slugs in me. One's lead,
the rest bourbon. The drink packs a wallop, and I pack a revolver. I'm
a private eye.