So yes, you should submit the true copy because it should be 'attached' to the translation (in the old days this was done by physically attaching sometimes with ribbons).We have to get our marriage certificate translated in English since it is in Urdu.
Yes, this is a bit weird because of course a scan can be split up, but their instructions have not yet caught up. You do not want to risk your app not meeting IRCC expectations on a technicality.