When Kathy says "aspiration pneumonia" and "lipoid pneumonia," I think she means that if the bird aspirates (breathes in) liquid or whatever is being tube fed, it can make the bird seriously ill because the body doesn't have a good way to get that stuff back out of the lungs. That's why anesthesiologists don't want people eating or drinking before surgery, so stuff doesn't get in your lungs.
If I understand her correctly "lipoid pneumonia" -- a pneumonia that resulted from aspirating (or breathing in) oil, could kill a bird... and I tend to think she's right, since it would probably interfere with the ability of the lung to transfer oxygen to the blood. I don't know if there would be any way for the body to clear the oil out of the lung, and since oil spreads out in very thin films, it might not take very much at all if it got into the lung for the bird to have a very bad, maybe fatal experience.
I don't know if I said that all correctly, but that's what I think she meant...