I said it because he does cryptography implementation professionally, if perhaps for insufficient reward. I'm sorry that's used to cast aspersions about him by attacking something I didn't say. Why exactly is Koch not qualified to consult on applications of OpenPGP as the main author of GnuPG (which I guess Purism are actually using)?
As I said, lots of people do cryptography implementation work professionally without being cryptography experts. In fact, I think that probably describes most implementors. So you haven't answered my question or supported the claim you made earlier.
I actually don't know whether he is or he isn't an expert, but the likely basis for the claim that he is --- maintainer of GnuPG --- isn't a valid one. People have funny ideas of where crypto expertise comes from.
(Disclaimer, or something: I consistently and reliably tell clients that while I'm comfortable testing certain cryptosystems, I am not qualified to design them. ['lvh, one of my partners, is, but he has formal training and I don't.])