There was a discussion about this before. It turned out that many stake pool operators didn’t make their stand-by back up BP as a stand by. After they realized this they switched to back-up BP as a node.
Concern was that it helps them win block battles if they encounter any.
If anyone can contact that stake pool operator just let them know that both BPs are running. Maybe they are not aware of this.
This thread on how to set up back-up BP could be helpful: