Yes, it's useful to quickly stash your work, switch to a different branch, do some quick fix, then go back to your original branch.
But in practice, what often happens is that your quick fix takes way longer than expected, and you don't immediately go back to your original branch.
Then you pull in some changes, maybe someone else pushed something to the branch you were working on, and you end up with a bunch of stashes on outdated branches and it's really hard to make sense of it all. Most of my working copies have at least half a dozen old stashes that I don't remember any details about anymore.
One approach to avoid this mess that git stash can lead to is to never use it, and just commit all your work before switching to a different branch. Clean up the current state of the repo, try to document your changes in the commit message, and commit them. Then switch branches.
You can always squash or rewrite the commits later, and it's a lot easier rebasing or merging a few old commits than working with stashes.
If you like stashes, please use them!
But I agree with the author, using them a lot can lead to a mess, and temporary branches are usually a cleaner way of saving your work.