A person that cares for coding will inevitably code more then 9-5 and consequently get familiar with new syntax

A person that invests time into their language knowledge will not have issues handling new syntax because they spend as much time as necessary to get familiar with the new syntax

So the criteria is being a 9-5 who doesn't particularly care about coding and doesn't invest time into their language knowledge

Not GP, but I assume the suggestion is that it's difficult to stay abreast of new developments within the constraints of a typical work day. Especially if your job utilises older technologies, as most do.