RESOLVED: Why is my tub overflow drain sealed shut?

[vtstav]

I took the cover off the overflow pipe in my tub to snake the drain and discovered that it's completely sealed closed, and it seems like it's been that way since it was installed... Can anyone help me identify what I'm looking at and/or how to remove it? I've tried unscrewing it, with no success, and it looks more like a knockout plug than anything, but smacking it with a chisel didn't seem to help much either. Do I need to use a hole saw?

 

[vtstav]

Still have no idea why it was designed this way, but I was able to use my utility knife to score the plug and then tear it out with some pliers. Looks like the overflow drain pipe is there, so hopefully the bottom was installed correctly! Lol