Could you charge it? Would the bolt carrier come all the way back, and into the receiver extension? If so, upper and lower center bore were okay, which would mean that it was okay.
I can get light to come through any upper and lower combo, even a couple maatched sets. It's gonna be there, to some extent.
I guess the only real test of it would be long-term testing. If the upper and lower center bore were off, you'd have some weird buffer face wear. At a minimum. Maybe even receiver extension wear, on the inside. Kinda like what you'd see with carrier tilt on a piston gun.