but why even mention "7 playable species" if you can customize your own? Why tell someone you have only 7 options when they really have 100+ options?
Because some people don't want to design a species. They want a quick start. That's the same reason why FO1 and Arcanum give you the option to chose a predetermined character een if most people would make their own character.
And actually they clearly said on their site that you can have 'seven playable races or a custum one'.