If the speakers are different distances to your listening position, the sound waves from the two speakers will arrive at different times and can cancel each other out, or amplify each other, at the various different frequencies. I suspect that is what was meant. Even moving your head a few inches can cause this with the higher frequencies.
I don't think that putting mono speakers above and below the TV will make it sound like the sound is coming from the TV. The sound will still come from the speakers above and below the TV. That's what mono is and does. You need stereo, not mono, to do what you want to do.
I don't think that putting mono speakers above and below the TV will make it sound like the sound is coming from the TV. The sound will still come from the speakers above and below the TV. That's what mono is and does. You need stereo, not mono, to do what you want to do.