This is what they should have done all along. Those that want to unlock everything with no effort, can do this (Or hell, use a cheat? Remember when we had those?). Those that want to play as usual, do not.
This is not something you should charge money for.
Know that if you allow someone to take advantage of you, they might make it a habit.
For example, if you purchased Windows Server from microsoft. You're limited in the number of CPUs and RAM based on the license and version. The features themselves are also limited by SKU. You can buy a cheap version of server and use hacks to unlock the feature to the same as the more expensive SKU but this is illegal as it's effectively stealing a product you didn't buy. The feature itself is technically fully there but is limited by the software license you used to install.
With the introduction of micro-transactions in video games, this also comes within legal territory for license enforcement.
However, this exploit in DS3 does not directly involve any of the microtransactions anyhow. It's simply a glitch or unintended feature and therefore could be classified as a defect of the game. This article misrepresents the situation because of the fact that this exploit does not allow you to get any of the additional features of the microtransactions without actually paying for them. If you could get the premium content without paying for them, that's when it could be illegal.