Interesting comments at article. Many saying that the code was poorly written.
This has been a continuing problem over the years. More and more coders are relying upon greater amounts of memory to accomplish their goals instead of streamlining the processes.
ANYTHING can be done faster in memory than on Disk if the problem is properly stated and the program is properly constructed. I can imagine, easily, situations that either could result in more rapid performance given (essentially) unlimited space on disk but not in memory. (a problem with “sparse matrices”)