No, you are missing the entire point.

His comment was a response to your post. Your post discouraged people from writing crypto, because they aren't qualified. This is where you were gatekeeping.

His response was, effectively: "well, you're so qualified, but you never said anything about how the industry standard library for crypto was swiss cheese for 20 years". He's basically saying that even the qualified people don't do a good job and that nobody should be discouraged from at least trying.

The point is that everyone is fallible and you went out of your way to prove him right.