That isn't the case in S2. It's pretty even so far.
That's not true.
North America: The more popular team has won both battle categories twice, one of them three times, and neither five times.
Europe: The more popular team has won both battle categories once, one of them four times, and neither five times.
Japan: The more popular team has never won both battle categories, has won one of them four times, and neither six times.
If the battles results were random, you'd see the more popular team win both types of battles about 25% of the time and neither one about 25% of the time. Instead, they lose both types about 50% of the time, and win both types about 10% of the time. There's clearly bias.