While it's certainly possible to write bad scripts in Bash like the example given, it's just as possible to write bad scripts in Python. All the time spent learning to do bash-like stuff in Python could just as well be spent learning to write better Bash.
I think the readability of the program is key as well. It's interesting that the author never included the full Python program. Based on the snippets I would expect it was longer and was definitely far more verbose. One of Bash's advantages in terms of working with files and shell commands is that most people already know how to work with files and shell commands at the command prompt and so the clarity is already there. If you replace all that with Python library calls all the sudden you're speaking a different language and comprehension will be slower unless your reader works with those Python libs just as often as they use the command line.
In other words, this may all sound good but be careful with this sort of advice. It's often counterproductive to go down this particular path