It's more of a case of where the differences between characters in western or eastern styles are quite different, especially in regards to the more subtle ones.
Most asians tend to think western characters tend to look the same, with this being especially true with younger characters (who end up looking like adults to them).
The things we pay attention to are not the same as the ones they do, and our methods of varying them are not the same as theirs. It's one of those culture gap things, where it takes some time getting used to, but once you understand it, you have a hard time reverting back to seeing things like the uninitiated.
For instance, I see a lot of variation in the faces in the OP pic, from things like the face length, softness/hardness, eyes and nose positioning/style, and so on. The differences aren't exactly subtle, but if I take a moment and try to see it as someone who's not familiar with anime would, I can see how the faces would look identical.
It's kind of like how westerners think all Asians look the same, and Asians think all westerners look the same.