Hi,
Yes, your understanding is correct. It takes up to 3 hours for imported conversion statistics to appear in your Google Ads account for last-click attribution. For other search attribution models for example like 'Data-driven', it can take longer than 3 hours. I would recommend you to refer to this
guide for more detailed information. As per the
help center article, conversions attributed using
attribution models other than 'Last click' are typically delayed up to 15 hours. In your case, if all of your conversions are 'Data-Driven' then those will take 15 hours to reflect in the Google Ads account.