This would most likely affect Bronze 1 and up since B3 is the one where you receives DEC. By "especially in higher leagues" meaning that silver 3 and up would have way higher advantages and the higher the league, the more the rewards rack up.

This makes sense because the jump on each league, for example, Bronze 1 = 6000 power but S3 = 15000 power, is too much. We might see a 5-7 dec per win again on s3 which would make sense.