If this is time critical issue, two solutions that might work...
I believe suppressing the feature will ignore it in the conversion. If this is not an option, you may need to do some extra work:
1. Export the file and re-import the file and delete the extraneous data. Then again, export the file.
2. Export the file without the curves as file1 and one with only curves as file2. Import file2 and delete extra curves. Export again.
1 is obviously simpler, but 2 may provide additional freedom by importing the curves separately.
3. You could try editing the STEP file to remove the extra curves.
Maybe someone will have a better answer. This is how I would go about it.