Please provide evidence that these concepts applies to Dealey Plaza.
You are joking, right? This is physics. It applies everywhere. Sounds reverberate off large flat surfaces, such as the fronts of buildings. The behaviour of sound is universal at any given location on this planet.
Which witnesses said echos were a problem in determining direction of the shots in Dealey Plaza?
They didn't, because they didn't realise it at the time. They hear a single sharp sound coming from a particular location, and they
cannot tell if that sound arrived directly from that location or if it was simply reflected from it. All they hear is a single 'crack'. They don't hear echoes as in the classic repeating sound fading off in volume so often prtrayed in film and TV. They don't experience difficulty in localising the direction of that sound. They simply lack the knowledge of what path that sound took to their ear from its
original source.
Imagine being deaf and blind and standing in the middle of a squash court and getting hit by a ball in the back of the head. All you know is that the ball hit you by approaching you from behind, but you don't know if it arrived there directly or after bouncing off a couple of walls first. When asked, you will say you were hit from behind by a squash ball, because you don't have any more information than that.
I repeat: how could different witnesses report hearing the same number of shots from different locations without this simple echo effect?