On our recent trip to WDW from LAX, we noticed this regarding TSA locks: After having your luggage tagged and boarding passes issued, passengers were directed to take their bags to the TSA screener (big Xray unit). Once there, you were asked if your bags were locked or unlocked. If your bags were locked you were required to stay until your bags had been screened. When asked, we told the screener that our bags were locked with TSA locks and they sent us on our way to the gate.
As someone who gets a bit restive waiting in lines, they were a good investment!