This was a design change that older fuselage kits wont have incorporated.
Both holes should be sized (or enlarged) for the insulating washers.
Also keep in mind that the continuity check is happening at a point in the plans where the other end of the cable has not been connected to anything yet.
If you have made connections prior to doing the check you might see the jack body connected to ground.
Any opinions expressed in this message are my own and not necessarily those of my employer.
RV-6A (aka "Junkyard Special ")