Let me ask a slightly different question in order to answer yours... Do you believe that Benzites actually "look exactly the same" or do they just appear to look the same to outsiders because they evolved on "the same geo-sphere"? It's not a practical question because it is not a practical problem.
I think they look exactly the same, because "looking exactly the same" and "appearing to look exactly the same" are two phrases which mean the exact same thing. If a vegetable appears to look like exactly like a cabbage, it looks exactly a cabbage, and, if I may be so bold as to guess, it may actually be
And yes, being able to tell each other apart is
a practical problem, one that won't solve itself and that won't be solved by pretending that it doesn't exist. Wesley can't tell Benzites apart, not because he's racist, but because he has no idea how they tell each other apart. That's why he's asking one of them, without any preconception and prejudice.
tl;dr: it's a false analogy. Benzites are not black people.