I think he's thinking more along the lines of PHP 5-8.5
That version 1-latest is understandingly highly different, but these are all decades old languages, which barely changed for some time, but are now all introducing new syntax.
Which I think makes sense, but it's obviously going to leave 9-5 devs behind that don't particularly care for coding and want to invest as little time as possible into their language knowledge.
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.
That version 1-latest is understandingly highly different, but these are all decades old languages, which barely changed for some time, but are now all introducing new syntax.
Which I think makes sense, but it's obviously going to leave 9-5 devs behind that don't particularly care for coding and want to invest as little time as possible into their language knowledge.