Is the 3.4 V6 considered a valve " interference " engine if the timing belt breaks?

yep it is an interference motor. Roy

Alldata doesn't show it as an interference engine, perhaps call your local dealer or Toyota North America customer service Phone: 800-331-4331 begin_of_the_skype_highlighting 800-331-4331

You are incorrect if you are referring to the 5VZ-FE engine. They are non-interference motors. That means if the timing belt breaks the pistons do not hit the valves. Mechanically speaking this means, the piston at top-dead center (meaning piston at its highest point) will not come in contact with valves opened up fully. I don’t know where you got your information, but please don’t spread false rumors on these publication forum cites. People rely on these websites to be fully accurate and it may cause them to have an unnecessary shop bill if you spread false information.