The difference is more on survival. A closed loop metabolism is indeed a good boundary marker. Viruses would fail this. But many have “closed but for a few critical dependencies”, and the argument here is that when life depended on metals like this, it’s more critical dependencies than closed loop.
Somewhere in there is a transition. But it’s poorly defined, and so the argument can be there was a bifurcation of sorts.
People love to put things into neat boxes so that we can somehow reduce them to a single concept.
Unfortunately the real world is usually a bit more messy than that. This is one example that makes it pretty obvious that our model is a little bit overly reductive, and at least to me the "Is this life?" question seems to have an answer that is on a spectrum rather than binary.