You need not worry about it. If your hinges won't budge, they are good to go.

The whole idea here is to get the CA to "Wick" into the slot. The deeper it goes, the better the bond.

Technically, the Thin CA SHOULD easily wick into the fiberous surface of the hinge, which will carry it into the slot (Even if the covering is not cut away). But if the CA is old and has thickened even slightly, it may need a little help getting in there. So by drilling a hole and removing the covering, it creates a channel for the CA to ride in and spread out sideways.

Probably the most important things about installing CA hinges are:

1) Flex the surface BEFORE adding the glue (And then do not close the gap again)

2) Use only fresh, THIN CA for good penetration