Right on, @swanderz. We implemented timestamp_add_sql and get_rows_different_sql as adapter methods for exactly this reason, so that you can override them in plugins.
See:
BigQuery redefines timestamp_add_sqlhere and adapts get_rows_different_sqlhere
see this draft PR: https://github.com/fishtown-analytics/dbt/pull/2790 not sure how to make this work without changing
dbt-core
... would love some ideas on workarounds: both short- and long-term.