To determine which refresh strategy is being used (incremental vs full), refer to the final section of the documentation: https://docs.databricks.com/aws/en/optimizations/incremental-refresh#determine-the-refresh-type-of-a....

According to the docs:

To determine the technique used, query the DLT event log where the "event_type" is "planning_information"...

Note:
There's a typo in the official documentation. To query the event log correctly, use FROM event_log_[NORMALIZED_DLT_ID]. Where [NORMALIZED_DLT_ID] is your pipeline ID with "_" instead of "-".

Look at the "details" column — if a **full refresh** is triggered, it often contains helpful insights into the reason.