"Can it really be scientifically justified though to say that a cockatoo has the 'goal' of opening the bin to get at the food inside? Or are we relying on bird consciousness or invoking some kind of weird causality here?"
By posing a question, the author nominally avoids making a blatantly false claim, but the intent is the same. In this case, the correct answer to the question is "yes" - it is not even close to being a problem.
The author then tries to suggest that the conventional explanation is in danger of inverting causality - "The cockatoo striving to eat the food inside the bin (a hypothetical future that hasn’t happened yet) causes it to open the bin in the present" -, as if all this learning was going on before the cockatoos learned that garbage cans often contained food, as if it would have been impossible to have discovered this before learning how to open the cans, and as if the development of foraging behavior is inexplicable under current concepts of evolution.
The author, of course, is well aware that there is no such problem, so, after attempting to raise doubts in the mind of the unprepared reader, he disavows all this, but in a way that tries to suggest that there is another problem: "Of course we can get around this if we appeal to consciousness and say that the bird has a mental model it has constructed around opening the bin. But that would restrict our theory of agency to things that have a brain. It wouldn’t make any sense to say that a plant wants to grow its roots to find water, or that an immune cell wants to chase after a bacterium in order to keep it from infecting the body."
Well, no, Jake, it wouldn't and it doesn't, but so what? The author apparently expects his readers to have already forgotten that this line of argument started with cockatoos' learning from observing one another, something noticeably absent from plants and immune cells.
The whole article is a chain of non-sequiturs constructed in this manner.