I'm sure its that so called "brushed" finish, and seeing it in real life is really beautiful.
Thing is, I had written off the Space Black Titanium (SBTi) myself back during S5 when it was new because i was in the "it looks too much like SG aluminum" camp of seeing pics of it, but when you see it closely in real life, no it actually doesn't. I would encourage anyone thats on the fence about SBTi to come into an Apple Store (if open in whatever country you're in) and try it on for themselves, only you can decide for yourself if you like it.
That being said, my main 'warning' about SBTi is, its trivial but anyway, if you're after a (Special) Edition Apple Watch that stands out among the crowd and looks markedly different, then Space Black Titanium isn't for you, you should instead go for the White Ceramic because I can see that one really stands out as different with it glossy all-white look (oh wait its been discontinued!). SBTi is in contrast much more toned down, and I think its an Edition Watch because of the unique "brushed" finish, in itself, is much more subtle and harder to notice from a distance. Only other thing is, I find it not as easy to match with bands, which again coming from SS, you could use pretty much anything with it except black-lugged bands and not second-guess yourself. Maybe the natural titanium is like SS and easy to match with anything?
But if that isn't an issue, go for it, the lighter weight on the wrist is really excellent, coming from SS, the Titanium material itself also feels nice and smooth when you pick it up with your fingers, fingerprint smudges on the SBTi are basically non-existent for me (compared to SS, the smudges really weren't great, I don't miss the high-maintainence!). I wasn't actually expecting Titanium to make it into the Series 6, but it did and I'm glad I got to try it, it's unique, but "subtle" is is the key word here