What does that even mean? Are you referring to algae consuming iodine and other trace minerals like iron? That's not optimizing water chemistry for itself, that's using nutrients that other algae might use. Maybe your iodine could get a little low if you don't do water changes but there are other concerns that would come for that but if it did even become a concern then dosing a little iodine is easier and cheaper than battling GHA.
Algae does nothing to kill corals except take away nutrients, grow over corals and shade corals, except for going sexual but with turf algae there is almost no chance of that happening. I've only heard of caulerpa going sexual but supposedly any algae has that possibility in nature. Point is that algae grows off of fish and coral waste making it beneficial to the system as long as it does not over take everything, that why we keep it contained in the turf scrubber.
People saying an ATS is bad for your system are typically just stubborn and don't want to admit that their way they have been doing it for years is not the most efficient. It certainly can be done without but an ATS is so much easier, cheaper and safer than many other methods.