We've got some pretty fucked up protectionist rules about what you can and can't do in/to your own home. It's nuts.
Now, nobody is actually watching most of the time, so you're usually fine, but it's as stupid as being illegal to replace a tap or existing light fitting. Every so often state governments review the rules and get swamped by trade associations who say the rules are there to prevent people being 'scammed' by untrained 'handymen' and are there for your own protection. This regulatory capture means that legally you need to complete a four year apprenticeship before you're allowed to change a plug! And another one if you want to do any basic water plumbing.
I wouldn't be surprised if what the guy did in this blog is strictly speaking illegal - for instance when it comes to data cables, you need to be a qualified electrician with data specialty to install them. You can plug ethernet cables into your computers yourself (wow! such privilege!), but if you install them even by getting some stick-on plastic conduit and passing the cable through that, you're in contravention and could potentially be fined, up to thousands of dollars. For sticking some plastic tubes to the wall in your own house.