Almost all of these are verbs or verb phrases: having this role gives you the ability to read all data, or write all data, or read all settings, or whatever. But you can't say that having this role gives you the ability to checkpointer. It gives you the ability to checkpoint, or to perform a checkpoint.
So I think the name is inconsistent with our usual convention, and we ought to fix it.
I was going to point out that pg_database_owner is the same way, but it is fundamentally different in that it has no special allowed access and is meant to be the target of permission grants rather than being granted to other roles.
+1 to rename it to pg_checkpoint or to some similar name.