That is true. Though it does make me wonder if cockatiels are actually partial ground foragers, and actually do eat from trees to some extant. One would think that if food in a tree was easy enough to access, they would probably try eating it. I once had a plum tree in the yard, where even the doves would just eat from the plums directly, just because they were easy enough to access.
plus if you look at pictures of wild cockatiels in trees, they do seem to have somewhat of a tree-dangling skill. They're able to hang on verticals branches.
On a somewhat related but almost entirely unrelated note, Lucy just proved her intelligence in the funniest way today. She climbed up the side of the playstand, up onto one of the highest points. However, she can't really go many places from there. So after a while, she just hung out. I started paying attention to Alex, talking to him and giving him scritches. Lucy started pacing the little spot she was on, trying to find a way to get down. Eventually, I gave in and decided to help her. So I put my finger in front of her to step up, and what does she do?
She lowers her head and asks for scritches.
She knows I'm a total sucker.