Theoretically speaking, will brewtan b do anything for me if I use demi-water and a stainless steel chiller?
It will bind up some of the undesirable proteins in the mash and boil that typically get removed through process points such as managing the correct mash pH, mash filtering, etc.
Also, as Bryan has pointed out in a few other places, it will give you some protection during packaging if your transfer process is deficient. Since fermentation has
eliminated O2, improper purging, transfer and packaging can allow for oxygen ingress which may be the catalyst for Fenton reactions, which Brewtan B should serve to mitigate.
So yes if you feel your purging, transfer and packaging stage is deficient. No if that stage of your process is sound.