I think people need to start breaking out of their current modes of thinking, and this article represents that. SEOs and Developers have more goals in common than people realize, and the approach is very similar. As long as we're talking about real SEOs, not these "guaranteed spots on Google" jokers, but people like John.
SEOs are there to solve a problem. The problem of course is much deeper than getting your site noticed. It's a vision consisting of strategies with the following goals:
The Basics:
1. Get the most traffic from search engines you can (obviously)
2. Ensure the traffic you get is from the people you want to reach
3. Ensure that you are providing what searchers are looking for
4. Try to build a brand and a vision people can understand
5. Build an audience that will keep returning to your site
Now these things are solid online marketing, sure but there are other goals too, that are more "hacker" in nature.
6. Perform analytics to find out which methods are working
7. Finding the most optimum content to attract new traffic
8. Find what landing pages are creating customers
9. Finding the most optimum paths to lead to engagement
Now this is starting to sound like hacking. We're all problem solvers here. This is gathering information and using it to get the best results possible. Like optimizing routines to save cycles.
As a developer, what are you trying to do for a company?
1. Build software that solves problems for the most people possible (usually)
2. Ensure that your software is targeted towards the people who need it
3. Ensuring your software is solving their problems effectively
4. Making the user interface as effective as it can be (usually by some form of analytics)
5. Finding the best ways to save cycles and utilize hardware (again found with analytics)
Do you see the parallels? This is exactly why I keep one foot in SEO, and one foot in Web Development, because they seem like entirely separate disciplines, but they have more in common than not. The name of the game here is optimization, and both fields strive for optimizing an experience.
Calling someone a software "hacker" means they learn as much as they can about a process and refine it. Tweak, push, pull and stretch. They optimize software to better meet the needs of those who use it. A SEO is a "hacker" because they optimize the website to meet the needs of those who use it. It's not about writing code, it's about finding ways to do more with less.
This is what I gather he's trying to say.