How do you know which parameter is used for ZeRO?

Quoting from here

If you’re migrating from ZeRO-2 configuration note that allgather_partitions , allgather_bucket_size and reduce_scatter configuration parameters are not used in ZeRO-3. If you keep these in the config file they will just be ignored.

How did you know? Because when I read documentation of deepspeed configuration. There is never any mention about which parameters will be ignored under ZeRO-3.