That's often true, but sometimes there is a cultural context. Knowing what kind of environment the author hails from casts light on interpretation more often than it does not, in fact. In this case, knowing that the author was not a Nigerian (for example) showed that the theory that "there are no light skin tones because the artist is not used to seeing them," is false.
Why do you need a theory to explain the skin tones? Why does it matter at all? What is so triggering for you about a web page without a depiction of a white person?
I'm not sure if it does, but the topic was being discussed so I joined in.
>What is so triggering for you about a web page without a depiction of a white person?
I'm not sure if "triggering" is the right word to use, but although I used to think that representation didn't matter (a la skin tone variants in emojis) I now realize that it's a nice gesture to be included in art asset packs and marketing material. Next time someone talks about how they added twelve different versions of a thumbs up asset I'll roll my eyes a little less hard. ;)