@Hunter_Han One thing to add to this discussion that I think @hawcad alluded to but did not mention explicitly is that there is an option on the JT export for "Include Precise Geomeometry".
When this is ticked, the export is the full mathematically precise model and is therefore easier to reverse engineer which I think is your worry. If this unticked, the export is just trianular simplified geometry i.e. a hole is actually just a crude polygon rather than perfect cylinder.
In addition, if you simplify your model using the visible faces first, and then export the simplified model as JT, it will then export something that is much more difficult to reverse engineer as the internal faces and whole parts you specify are gone.