This was true in the mid 2000s, but isn't true on most modern cars. Most modern cars have a Gateway module which sits between the OBD port and the Powertrain CAN busses which the OP is reverse engineering.
These Gateway modules only allow specific diagnostics-related messages through to the various backing buses.
Now, generally the security on the Gateway module itself isn't great, and diagnostic protocols also aren't very well secured, so there's certainly havoc to wreak. But it's not as simple as "plug in a dongle and send commands" - to do what OP is doing, you need to tap into a wiring harness that's usually buried a bit higher up in the dashboard, at least :)
Usually either the Gateway or the control module itself will disallow sensitive UDS commands like the Hard Reset from the article, as well as adaptation / basic settings and output testing commands which are not safe given the current parameters, as well - for example, I doubt you could send UDS Hard Reset to the gear selector module while the car is moving.
These Gateway modules only allow specific diagnostics-related messages through to the various backing buses.
Now, generally the security on the Gateway module itself isn't great, and diagnostic protocols also aren't very well secured, so there's certainly havoc to wreak. But it's not as simple as "plug in a dongle and send commands" - to do what OP is doing, you need to tap into a wiring harness that's usually buried a bit higher up in the dashboard, at least :)
Usually either the Gateway or the control module itself will disallow sensitive UDS commands like the Hard Reset from the article, as well as adaptation / basic settings and output testing commands which are not safe given the current parameters, as well - for example, I doubt you could send UDS Hard Reset to the gear selector module while the car is moving.