Yes, both the article ("A Solution of the P versus NP Problem") and the comment on it ("The proof is wrong") are written by Blum. It's both very nice and honorable that the author is pointing out his own errors publicly.
In other words, he might not have been building up the hype but instead was making sure he wouldn't have to retract a paper with a (more or less) obvious mistake in it. That's how science should be done rather than behind closed doors !
Many results in math establish a famous theorem by proving something more abstract that "easily" implies the famous result, like with Fermat's Last Theorem.