[Dfariswheel]

The reason it has no cut for the pin is so you can set the head space on the barrel before the cut is made.

Most of the older AK kits came with the original barrel and trunnion.
On those, all you had to do was press the barrel in until the cut in the barrel lined up with the hole.
Since the ATF stopped imports of kits with original barrels, the barrels are not the original and are not fitted to that trunnion. You have to fit them.

On the AK rifles, the head space is set by using a head space gage set and pressing the barrel in until the head space is correct. Then the cut is made by using a drill to carefully drill through the pin hole, which cuts the groove in the barrel.

In other words, you have an un-head spaced barrel that's never been properly fitted to that barrel trunnion.
You have to head space it to make it safe to fire.

Do a Google search. There's several sites out there that show how to use head space gages to set the head space on an AK build.