The article is from 8 years ago. They wrote the game in 2004. Regarding profiling tools, plenty existed both 8 and 16 years ago. We used a tracing profiler in our commercial work to identify un-exercised code paths to either let us know the code couldn’t be reached (dynamically because static analysis said it should be reachable) or that our tests were incomplete. I’m not sure the status of free tools at the time.
I think they were short of time (as the post mentions, everything Lekktor happened within a single week; this is the most impressive part of the entire post) and had rather special build environments that are unsuitable for many profilers. For example the kkrunchy executable packer [1] used by Farbrausch doesn't pack the DLL sections at all, so any instrumention relying on them will be ruined. Such things.
I get that, but even the simpler side of the instrumentation tools we used wouldn't have been a problem to use for them. The most basic one basically just (with knowledge of the language) inserted outputs at function entry/exit and branch points (if, else, loops). However, it was a commercial tool that did this for us as part of their suite of tools. I have no idea what the status of open source/free tools would have been in 2004 to do the same thing.
