Someone can correct me if I'm wrong, but I don't believe that the last year of Horford's contract is fully guaranteed?
“Only $14,500,000 guaranteed in 2022/23, HoopsHype has learned. He would get $19,500,000 guaranteed if his team makes it to the NBA Finals in 2019/20, 2020/21 or 2021/22. His 2022/23 would be fully guaranteed if his team wins the NBA championship.”