[Jim S]

Actually I think my term is READ RULE 2, READ RULE 2, READ RULE 2, READ RULE 2. (four times)
But yes it certainly applies here.

You are totally correct.
Go back and ask them: When does the momentum rule apply? (When you CARRY a ball that you have caught into the EZ).
And, when does a catch occur. (When you return to the ground inbounds with the ball in your possession.)
Therfore the monentum rule doesn't apply.
Then give them the address for this board if they still want to argue about it!