Some types can seem like others superficially,but the depths and motivations are all too different (the tests aren't yet complex enough to deal in such things...which is why they're unreliable.)
Then there's the complexity of the tri-type.The three fixes (gut, head, and heart) can give the primary type a flavor...that appears to be an all together different type on the surface.
I don't feel like getting deep with it,but it's good to remember that the literature (especially the tests) are most indefinitely Not the end all,be all. The enneagram is above all,a theory...still being explored. One's understanding of it never really ends.