Earlier quoted context omitted.
I thought there were a few required proteins that were very hard to supply in the body without an animal source
All amino acids originate from non-animals (plants, microbes). Where do you think other animals get their essential amino acids? They eat plants or eat an animal that ate plants. All plant proteins have all of the essential amino acids. The only truly “incomplete” protein is gelatin, which is missing the amino acid tryptophan, so the only protein source you couldn’t live on is Jello.
And there are lots of plant sources that are missing or insufficient in essential amino acids. Beans, for example, are lacking in methionine, which is why corn and beans are eaten together in some traditional diets.