It’s open about the skew: “All the major and many of the minor living branches of life are shown on this diagram, but only a few of those that have gone extinct are shown.”
Extinction is overwhelmingly the deep reality, compared to which the survival of species — the selected phenomenon — is scarcely more than a rounding error. Through a reflexive, lucid, secondary selection the culled, blasted, and gnawed tree of terrestrial life is edited into the attractive flowering shrub we see in the diagram. It shows us what our illusion looks like in detail.
Survivor or selection bias is a hugely important frame. It absorbs the whole of anthropic reasoning in principle. To produce a display of life on earth that realistically incorporated it would require overcoming a range of psychological and epistemological obstacles so profound they reach the very root of the biological enterprise and even human intelligence as such, but only then would we truly see where we come from.