I think the point that fubarobfusco was trying to make with that was a partial refutation of the "narrowing circle" thesis that says we care less about people not like us today than in the past. S/he was trying to say, "we haven't stopped caring about anyone we used to care about, we've just stopped believing in them. If we still believed our dead ancestors had feelings, we'd still care about them."

You're correct that all that matters for the question "did ancestor-worshippers care for non-humans" is whether the ancestor-worshippers thought their ancestors were human.