I agree with this definition but power and traditional specification are not part of "pro" definition because these parameters are so user specific.
They are indeed user specific but answer to the question on how machine can make an user pro.
What is not user specific is for example reliability and ergonomics.
I would argue that even this is user specific. Reliability is a broad term. As an end user I care if a machine is reliable for my needs, not if it is reliable in general. Ergonomics highly depends on one physical needs. For example I have small hands, have wrist issues, have back pain issues and I have myopia. So for my needs I need big screen enough so that I don't put a strain on my back/neck and to not exhaust my eyes. On the other hand I have small hands so I do not need the biggest keyboard out there.
For example, a $50,000 MP would not add any value for me to earn more money over an iMac or iPad. In fact, the MP would be an economic burden and hence an unprofessional choice. For someone else such MPs as necessary and would be the correct professional choice. We all however need reliable computers with good ergonomics to earn money.
We do need them but we all put different values behind ergonomics and reliability. For example iOS management issues (with reloading tabs/apps) makes the iPad for me quite unreliable machine. For others the noise the laptop/desktop produces is sort of unreliability.
In my case power does relate to reliability as I need good RAM management. I might achieve this with more RAM.