That would be an ABSOLUTE nightmare to clean and maintain. The dirt will flake off whenever you even try to clean it. And forget about disinfecting that enclosure...not possible with all the semi-loose dirt and nooks and crannies. Not to mention that flooring adhesive is far from non-toxic, especially when heated.
There are other ways to achieve that sort of look...all of which are safer. Read up on creating grout rock structures...with painting and grout, you can make a real looking rockwall. Its not that hard, and will be much more durable then whats in that video.