I'm a huge Kurt fan and have wanted to get his signature on one of this classic books. This is his style, but it looks a bit off to me, like someone trying to copy his style. But I haven't done an extensive study on his signatures. Some people sign quickly, are drunk, or they're walking as they sign...and all kinds of reasons a signature could look a little off. That's the long way of me saying -- I just don't know.
I got KV several times back in the day. TTM his signature was perhaps a little neater, but the one you showed is not particularly suspect to me.
I'd keep comparing to others until you are confident one way or the other.