But that's normal - emotionally boding with a farm animal you intend to slaughter and eat is indeed counterproductive.

The trope is about something different - it's about intentionally making a subject bond with an animal over long time, as with a close friend, and then finally making them kill the animal as a final test of loyalty.

Doing that in real life, and for no good reason, is just sick.

It is, those people think this practice will speed up process of that bond being understood as counterproductive.