Yes, this gives a misleading view of the relationship between citrus fruits.

This diagram (on the Wikipedia article for Citrus) gives more information: https://en.wikipedia.org/wiki/File:Hybrid_origins_of_Citrus....

Is not so simple, there are TWO grapefruits. One is an hybrid, the other is one of the four fantastic ancient Citrus species, that are the grand-grand-grand-parents of (almost) every known fruit from that family. "Everything", from Uglyfruits to Blood Oranges to Key limes is an hybrid except a very few wild species

In general this view doesn't do a good job of explaining citrus fruits. There are a huge variety of hybrids mostly deriving from combinations of the mandarin, pomelo, citron, and micrantha (lime).