It's not. Really, it just isn't. The level of detail and manufacturing accuracy/tolerances that go into a Sebenza just aren't there in the Slysz. "Feel" being such a subjective thing anyway, one could argue that all day long, but no one can honestly say that the Spyderco Slysz is exactly 1:1 with the Sebenza. Pivot construction alone renders that a moot comparison.
Now, is the Slysz a really nice knife? Sure is. I bought one the moment it came out. Aside from the crowned blade spine and beautiful stone wash finish on the blade and handles, I did not personally feel that at $300 it was quite worth it. Again, that's highly, highly subjective.
I found the action out of the box to be fairly pedestrian, i.e. acceptable and likely to break in, but a bit draggy and gritty; typical production knife feel. The design is understated and cool, but it just didn't feel "special" to me. And when the street price is $300.00, it really has to have that for me to keep it. Conversely, I've never owned a Sebenza that did not feel like it was special or worth every penny. To me, I really didn't think there was enough to the Slysz to justify the price and it left me feeling a little down on it. Again, there's nothing "wrong" with it, but a "Sebenza killer" it will never be. And it's not supposed to be anyway.
Of course, I say that and then promptly drop another $300 on the Rubicon...which I absolutely do feel is worth the street price. There's so much nice detail there, and it's so well done.
Also, I think one of Spyderco's friendly competitors in the U.S. have recently upped their game in the Ti frame lock biz; one of which I had recently purchased before the Slysz, and for $100 less, I honestly feel like I got a lot more.
So much of this is subjective though...if you want a Slysz, buy one. If you want a Sebenza, get one. But they are just not the same thing, and I think that's perfectly ok. I think the question is will you personally be happy with the Slysz for what it costs? Everyone evaluates that differently.