Two structurally and functionally indistinguishable systems,
one natural and the other man-made,
their full causal mechanism known and understood:
What does it mean to ask:
"But what if one of them is really alive, whereas the other is not?"

What property is at issue that one has and the other lacks,
when all empirical properties have already been captured?

Vitalism sounds like the other-minds problem
-- and may be the other-minds problem:

the animism at the true heart
(soul) of vitalism