`/worldborder set` does not respect tick rates higher than 20

Step:

1. Stand on the world center.

2. /worldborder set 20

3. /tick rate 40

4. /worldborder set 10 10s

5. See the border contracts in 10s. (expect: 5s)

While in /tick rate 10(any num under 20) , it works well.

In fact, this bug can be even found in 1.21.11.