Z-Bar question regarding hole under clutch rod post

Here are pictures from both the '65 service manual and parts manual. Notice the hole does not appear in the parts manual (pg 6-2), but does show up in the service manual (figure 5), with nothing is attached to it. It certainly could be a spring hole, but why doesn't a spring show up in either picture? I can see the possibility of a spring there, but what would it attach to, and why would it be needed? I'm thinking there may be an other application this Z-bar is used for, but I googled the part number for it (2781876) and the pictures that come up all look the same and they all have the hole, and they are all for '64-'66 A body. I'm not trying to beat this thing to death but it sure is a mystery.

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