strange CREATE INDEX tab completion cases

These two tab completion pieces look strange to me:
   /* If we have CREATE|UNIQUE INDEX <sth> CONCURRENTLY, then add "ON" */    else if ((pg_strcasecmp(prev3_wd, "INDEX")
==0 ||              pg_strcasecmp(prev2_wd, "INDEX") == 0) &&             pg_strcasecmp(prev_wd, "CONCURRENTLY") == 0)
     COMPLETE_WITH_CONST("ON");    /* If we have CREATE|UNIQUE INDEX <sth>, then add "ON" or "CONCURRENTLY" */    else
if((pg_strcasecmp(prev3_wd, "CREATE") == 0 ||              pg_strcasecmp(prev3_wd, "UNIQUE") == 0) &&
pg_strcasecmp(prev2_wd,"INDEX") == 0)   {        static const char *const list_CREATE_INDEX[] =        {"CONCURRENTLY",
"ON",NULL};
 
        COMPLETE_WITH_LIST(list_CREATE_INDEX);    }

They appear to support a syntax along the lines of
   CREATE INDEX name CONCURRENTLY

which is not the actual syntax.