Obviously corporations are a legal fiction and not biological human entities with inherent intelligence and agency.

They are tools to enable the wills of specific human beings, so the comparison seems fair?

What comparison do you think the parent comment is making? They just vaguely gesture at corporate personhood and say "what about that?"

My best reading of it is "can 'they' say that corporations can author works?" and excepting works for hire, no, "they" can't.