The usage of "same" in the description can be a bit tricky to parse, but a look at the test cases sort of helps clarify things.

The description says, "...all of them (the other elements) are the same, except for one single number."

In your example case, although 2 is the single number, 1 and 3 are not all the same. Therefore, it would not be what the kata is testing for.

In other words, the kata is looking for examples that take on the template of: [x, x, x, x, y, x, x] or [y, x, x, x, x] but not [x, y, y, z, z, z, z, z, z].