I don't have an answer for you,
You can suppress what you do not want to export,
when you do a save as, and select STP, check the export options.
I would export the file then import it right back in SW to see if it is what you are looking for.
Is your end goal to have something that someone else can't measure? Maybe exporting as an STL would do what you want.
Select only the surfaces (ctrl select) or surface bodies (from the surface bodies folder) you want to export; Save as; STEP;... a "Export" menu will pop-up asking if you want to save Selected face or Bodies or All bodies.