I'm reading the parent post not as "you say that hunting is permissible if you're hunting for survival" but instead as a claim that this cruelty is justified if and only if you're hunting for survival.

The same would apply for slaughter - if it would be a survival matter, then any methods would be permissible (i.e. some of the more cruel traditional approaches) but since it is not, it should be mandatory to use only the less painful approaches to slaughter.