> Is it just an attempt to get us to re-evaluate our emotional attachment to some species (e.g. dogs) in comparison to others (pigs) - when it turns out that upon further analysis there's no objective justification for doing so?

Yes it's more just this. It might but I don't think it has a particularly large philosophical underpinning, it's more just used as activism

elwooddogmeat.com is a good example of its use in my opinion.