On my ipad I got 7.73 on level 4. On my mom’s phone I got 7.68 on level 4. On my iPad I got 4.93 on level 1. On my mom’s phone I got 4.88. This shows that a phone makes the ball go a little bit faster. Why?

I would say it's just easier to swipe on a phone. Since the screen is smaller, you have to swipe a shorter distance to achieve the same speed.