db, alignment of the cam marks is relative to the crank pulley. At some point in the rotation the crank pulley will be at 0T and at some point the cam marks will align. Hopefully both occur at the same time. For the most part this is determined by the length of the chain. There are other factors such as wear in the sprockets and thickness of the head gasket. Given all that, it's a wonder that on an engine with over 100, 200 or 300K miles you can get everything to align to within 1 degree without 'cheats' like offset keys.

Having said all that, I don't follow your question The tensioner has nothing to do with static cam timing. Its job is to keep the chain taut so the crank can pull the IP and cam without the jerkiness associated with the natural rest positions. It's also there to take up the slack designed into the timing system to allow the engine to be serviced without breaking the chain.

Sixto
95 S420
87 300SDL