New to this, looking for opinions

This is what my son is being taught.

Assuming you son is strong enough to make the throw down to 2b, I see no point in "gaining ground" with his footwork.  The thrown ball will move faster than his feet.  On the other hand, if the coach is talking about a follow thru and following his throw then I wouldn't have a problem. 

I am not an expert but it is my understanding that the best technique is to "replace the feet" as the ball is transferring from glove hand to throwing hand.  Proper rythym is important during this process as it should be "step...step...throw" in an even cadence.  As the ball is being transferred, the catcher should replace his left foot with his right and square his left foot around so that he is lined up to throw to second.

 

I found a pretty good video that explains it.

 

https://www.youtube.com/watch?v=FO4AMZXl-AE

 

 

What the OP describes is how my son is taught by his coach who caught 8 years in the minors.  Hips and everything stay square to the target the entire time.  Gaining ground is desirable with this technique as I understand it.  Everything is in a straight line so ball goes straight which for a natural sinker baller like my son is a needed adjustment when he is catching vs. pitching.

 

It looks very "robotic" to me but it works for my son. 

 

 

Unless your son can convince his coach a reputable expert taught the current footwork I suggest he do as the coach requests.

Look here...

 

Catching 101

 

or here...

 

New England Catching Camp

 

They both come highly recommended.

 

The issue your son may be having is where he is taking his jab step.  If it is in the middle of the clock, good.  If he is stepping to 9 o'clock, your son may be losing momentum to his target.  In other words his weight is shifting towards the right hand batter's box, rather than directly at 2nd.  It's a subtle thing, but you want to minimize anything that takes your momentum off line to your target.

This video is mis-leading.  The narrator repeatedly says, "replace your left foot with your right foot."  This works just fine with a LHB in the box and,  not surprisingly, almost all the examples in the video are catcher's throwdowns with a LHB in the box.   Whereas, with a RHB in the box, a catcher can't shift their right foot all the way to where their left foot was.  If they did, they would  drift too close to the batter. .

I think the key point is gaining ground with the right foot towards 2B and following through.