While referencing real life pictures is the best way to learn poses and the way anatomy is set up, referencing off pictures can help someone A LOT. Sometimes photos/images of real life are difficult to draw. Like for example, a cat paw. One might reference off a real life cat paw but have trouble shaping the lines to actually look like the paw if you catch my drift. I find it easier to reference off both drawings and irl images!
The idea is to learn how stuff works by looking at life; once you’ve studies many cat paws, you’ll know how to manipulate them yourself in any angle/pose/whatever. Reffing off of art is probably quicker tho