Pool heaters are usually tapped outside right off the meter, and remain outside. I would expect there to be a shutoff valve right at the start of the run, near the meter.
Did you get a card from the first guy when he did your dryer?
While I would never try to install my own gas line, it is of my opinion that TSSA this is nothing but a money generating scam in the back pocket of the service companies.
The latest regulation just enforces that. The new TSSA code was that the plastic venting must have a certain marking on it. Otherwise when the appliance is replaced, the venting must be replaced. If it hasn't melted in the past, why is it an issue now?