Typically, these forms retrieve data from previous entries as expected. However, forms can also function as standalone documents, independent of any workflow. In such scenarios, one would not expect them to pull historical data, yet they still do.
Even if the form isn’t part of a workflow, it’s still working as it should. A standalone form can pull in data, whether it’s using copy forward or has pre-populate mappings set to something like 'last completed.'
If you want to keep copy forward as an option but don’t always want it to bring in data, just set it to 'choose copy forward at runtime.' That way, when you open the form, you’ll get a pop-up asking if you want to copy forward, just hit 'no' for standalone forms.