He questioned it for a few minutes, and then the defensive coach wanted an automatic double play.

The OM asked why it was interference if he didn't even touch the ball or the fielder. My partner answered that he denied the fielder an opportunity to see the ball sooner and make the play. He called it, but the shortstop continued and made the play. He took good command of the call and the description. Good command for a kid, that is. ;)

The defensive coach wound up being more of a pain in the a$$ about the automatic double play (no chance in hell of two on this play).

Please describe a specific play where that happens -- I'm having trouble envisioning the BR hindering F3, but F3 "successfully fields the ball" (by which I assume you mean catches the throw).

Yes. Doesn't the provision for runner's lane interference deal with F3's ability to field the throw?

Example: Bunt down 1BL, F2 fields, throws, B/R is inside the runner's lane about 20 ft from 1B, F2 successfully threads the needle by throwing the ball over B/R's left shoulder and F3 catches the ball for a 2-3 putout.

If the ball goes off of B/R's helmet and out into RF...you have running lane INT right?

So...I'm asking the other poster if he would call it before he saw the result of the attempted play?

If the fielder had to pull up instead of charging a ground ball (which any coach with 1/3 of a brain should be teaching his kids to do) to avoid a runner intentionally hovering in front of a grounder, it doesn't matter how cleanly the ball was fielded.