Google: 90% of our engineers use the software you wrote (Homebrew), but...
IMHO, I don't think it requires any practice to be able to invert the binary tree. It is so trivial that it only requires a very basic level of programming skills. I agree whiteboard is generally broken, but for this particular case, I don't think Google is doing wrong. We can think another way, if some company hires people based on his reputation instead of the ability of doing actual work, I don't think it will survive. In this particular case, you just didn't show your ability of doing actual work, that's it. I am glad to see that Google prefers ability of doing actual work to reputation.