create table explicitly mention that unique|primary key constraint will create an

Hi. minor doc issue.
create table s1(a int, constraint s2 PRIMARY key (a));
create table s2(a int);
ERROR:  relation "s2" already exists

https://www.postgresql.org/docs/current/sql-createtable.html#SQL-CREATETABLE-PARMS-UNIQUE
maybe for the following 2 sentence
"Adding a unique constraint will automatically create a unique btree
index on the column or group of columns used in the constraint."
"Adding a PRIMARY KEY constraint will automatically create a unique
btree index on the column or group of columns used in the constraint."

maybe we can mention that: the unique btree index name will be the
constraint name.
also is "a unique" or "an unique"?
I personally thought this part is obscure.