No, the OP’s argument is assuming that the lives of farmed animals is net negative. It’s saying that farmed animal welfare might at most be neutral, which would mean that, on expectation, farmed animal welfare is harmful. Nevertheless, it would be less harmful than ignoring farmed animal welfare would be, which means farmed animal welfare is still net positive.
Meanwhile, the argument in your link argues that farmed animal welfare may be net negative, but it relies on the opposite assumption that the lives of farmed animals may be net positive.
No, the OP’s argument is assuming that the lives of farmed animals is net negative. It’s saying that farmed animal welfare might at most be neutral, which would mean that, on expectation, farmed animal welfare is harmful. Nevertheless, it would be less harmful than ignoring farmed animal welfare would be, which means farmed animal welfare is still net positive.
Meanwhile, the argument in your link argues that farmed animal welfare may be net negative, but it relies on the opposite assumption that the lives of farmed animals may be net positive.