We all have unique biomes in our gut, and they're tailored to us. If you lose it, eg something kills all your gut bacteria, you will be very sick. The only cure is to have a transplant from a relative. Literally fecal matter is taken from a donar, pureed, and shoved up your wahzoo.
https://en.wikipedia.org/wiki/Fecal_microbiota_transplant
My point? Your and my gut bacteria may need meat, and it could be why some cannot do the vegan thing. If your gut bacteria isn't happy, you aren't. And you can't just swap that out.
You can probably just put some poop in a gelcap... (this is not medical advice!)
It's precisely why they seek a close relative.
Adding some additional gut bacteria doesn't replace everything you have. Otherwise, you'd get sick from eating a salad someone else prepared, and ingesting some of their bacteria. The peanut thing may be introducing an additional bacterium which perhaps processes peanuts in a better fashion, but without supplanting anything?
So I won't say you're wrong. But without trials I won't say you're right, either.