That is appalling I would go back and make them change it and stand there watching them correctly set your TPS and if don't want you to come into workshop tell them to do it in the door way so you can watch.
To many workshops use the excuse of lack of insurance coverage to keep people from making sure they do their job right I know don't take the bull rap and just tell them "I will be and am capable of keep myself safe if the tech are doing their job properly their should never be a safety issue" what did we ever do before OH&S BULLCRAP it is just poor excuse for people not using common sense, rant over