This.
It'll make no difference whatsoever to the safety or accuracy of the firearm.
The grooves on either side of the center portion were cut a little deeper than they needed to be, or the firing pin hole is off center a wee bit, maybe both, but its much worry about not much.
Like as not, the repeated cleaning knocked out the thin material that would have been left after the two cuts were made. Or you simply didn't notice the holes before.
If you want some dry and uninteresting reading, start researching Geometric Tolerancing, and the causes and effects of "Ganged Tolerances" and how they can make life....fun.
