I may be missing something, but I haven't seen a "gas water heater" in any of the pictures. I assume this is over a crawl space, otherwise running a toilet arm on an angle like that would be somewhat destructive. Pictures of the piping ABOVE the floor are useless. We need to see what is UNDER the floor.
He's talking about the rusty hulk mounted in the left side of the wall. "Gas heater" (i.e. heater of air) not "gas water heater".
My question is whether he is planning to perform surgery on the gas piping; potentially-dangerous to assume that it's permanently capped-off.