Security against what?

I do it for the simply reason that it's easy to break a pin if you load the end. If you try to shear it, hard to break.

Since the cam sproket is thick than the bushing. If you drill all the way through. The bushing will not rotate but it is free to walk forward against the cam bolt washer. When if floats to the rear, that's a good thing. It places the camshaft dowel in a shear load. Strong.

When if floats to the front. You are now driving the camshaft with the tip of the dowel.

So drill the hole only deep enough to keep the bushing near the back of the sproket. I'm sure this has been overlooked a million times but shear load is why I only drill part way through.