Here https://playhearthstone.com/en-us/battlegrounds?sort=attack&tier=1&viewMode=table
you can see some sort problem.
Here is a picture with explanations https://i114.fastpic.ru/big/2020/1010/3e/c9bc4646d13113f227ffb45eae22b73e.png
I did some tests and it looks like sorting in most cases divides items into two groups and then sorts them separately. But in some cases, sorting works correctly. Apparently this bug does not always appear.
I hope it is not a difficult problem and it will be fixed.