They can hit there if forced to the left before tightening and releasing the pin best way to avoid it is to make sure the bolts are finger tight enough that the tensioner can slide from right to left once belts in place and all the idlers are on push the tensioner across with a screwdriver don't use a pry bar or be heavy on it it should move with relative ease .
Tighten the bolts to hold it in the left position and use a torque wrench to specs otherwise you will pull the thread. . Then remove the pin holding the piston .The crushing of the tensioner usually happens when some one is heavy handed with a prybar trying to push the tensioner to the left because they pulled the pin out before realizing that it has to be moved across and tightened beforehand .