Isn't a PK automatically a proper unique indexed key

I'm checking out some newish features of Apache Derby for my Java EE app. IntelliJ provides helpful shortcuts for creating a simple DB schema. After a few clicks I have create table "Names" ( id int generated always as identity constraint NAMES_PK primary key ); This should, to me, create a proper lookup table, hash or map, for the PK. If I add the criteria that PK needs to be unique (?) create unique index NAMES_ID_UINDEX on "Names" (id); So my Q is, does this change the how the PK lookup is implemented? The docs are quite unclear on this. This is Derby 10.15.2.0.