

It’s a nice gesture. But so long as we keep not holding Trump, his administration, or the UDoJ to account for breaking laws whenever it suits them, it’s security theater. At the very least it’s not hurting the voting process and may hold some immediate benefits in getting more participation.

What it comes down to isn’t just the soul, but knowledge itself. Knowledge is the ultimate power of the series. Or, so it seems to make argument for. We see essentially all throughout the story that knowledge and science-like discovery brings great wonders and horrible terrors. Animals don’t hold much information or memory. It’s not that they couldn’t use animals for philosopher stones. It’s more likely an efficiency problem, or like you pointed out they’d just use animals.
Another reason why human transmutation is prioritized is because it’s a lot more taboo. You’re not gonna feel the same stakes watching a show where some alchemists make a philosopher’s burger out of cows and use it to get their bodies back. Tada! story over. Humans don’t care much for animal life the same way. We already benefit from the mass slaughter of animals. It’s when humans see themselves in the slaughterhouse that horror is properly introduced. It compels the viewer and the main characters to find more ethical alternatives (eventually discovering that with alchemy, there are no ethical alternatives).
That’s why the ending is about sacrificing knowledge to regain a human body and soul. It brings the conversation full circle.