Pre-turbo or post-turbo doesn't really matter much. The purpose of the pyro is to give you an idea of internal engine temps so you don't melt a piston.
Banks Engineering engineers a lot of high performance aftermarket turbo kits for diesel pickup trucks. They place the sensor post-turbo too. But they also know the drop in temps from the exhaust port, through the turbo to the sensor at different engine loads. They have done the research and can say "Don't go over XXX degrees or you risk damaging your engine. You can intermittently go above YYY degrees." They even build a color coded range into their gauge faces.
If you don't have the time or resources to do this kind of engineering and testing it's much easier to get more accurate reading by placing the sensor pre-turbo. That's why so many people here recommend it. It removes any of the variables/unknowns. Fueling rates, manifold design, exhaust size, turbine A/R, thermal mass, water cooled center sections housing and other things contribute to a variable drop in exhaust temp through the turbo. So when people here recommend "Don't go over X degrees with a sensor post-turbo" you can't always accept it as the gospel truth. It's just a guideline.
