Clarification required in dbt docs

The problem I’m having

Its mentioned here that dbt-redshift will do append in incremental model by default when merge strategy is not provided. But In our project its doing delete+insert. Are the docs correct? Or am I missing something. I have pasted the sample config below

Some example code or error messages

    materialized = 'incremental',
    enabled = true,
    sort = 'date_time',
    dist = 'x',
    alias = 'raw_table' ,
    on_schema_change = 'sync_all_columns',
    unique_key = '(x||y)',