Hi bunker,
It seems unlikely that the deordorizer could make its way into the fresh tank. If the deodorizer were migrating backwards through the water system, AND you had a problem with the internal check valve built into the water pump, I suppose you might get some into the fresh tank. BUT, you would also have deodorizer coming out all of your faucets and shower. And your fresh tank would be overflowing from water going backward through the pump.
If you're sure the deodorizer is actually migrating into the fresh tank, I would recommend disconnecting it until the dealer can revisit the installation. You might also visit the website for the dispenser manufacturer to see if you can download installation instructions. Then you could compare the manufacturer's instructions and pictures to what the dealer actually did.