It would only be a No-True-Scotsman argument if the original statement of Linus' Law were, "In an open-source project, all bugs are shallow" and someone were now trying to claim that GnuTLS wasn't open-sourcey enough.
In reality, the law is about code that has many eyeballs on it, and it's a fair argument to point out that evidence suggests GnuTLS didn't have that many eyeballs on it.
Can you present some of that evidence about the lack of eyeballs on GnuTLS? Because my point is that the right kind of eyeballs were not on GnuTLS; my point isn't compatible with this supposed "law".
In reality, the law is about code that has many eyeballs on it, and it's a fair argument to point out that evidence suggests GnuTLS didn't have that many eyeballs on it.