Correct, all purchases in the time window will count in the reporting, not just those who clicked or clicked and made a purchase in that session. There are future updates for more precise conversion tracking in the works.
You could create a report limited to those who clicked the abandon, that will make it more accurate, but it will still be directional reporting (they could click and buy later, or start a whole new purchase unrelated during the conversion window after the abandon click). A shorter conversion window equals more accurate conversion reporting.
If you are using GA or other Website analytics, you could pass values in the url for tracking (same would go if you are using a data warehouse like snowflake to create custom reporting).
