He also wrote a well known book on the subject: 'against the grain', where this argument is put forth. Wikipedia has a summary of the book: https://en.wikipedia.org/wiki/Against_the_Grain:_A_Deep_Hist...
There are examples of large scale public engineering works with and without observable central authority throughout archaeological record around the globe. So just "having walls" is not sufficient implication of central authority attempting to control the population.
IMO in the specific example of Against the grain the central authority thesis is pretty solidly framed. But, it does not aim to be a generalizable theory, nor IMO should it be viewed as such.
Now it always possible to argue against the applicability of any rule, there are exceptions to rules. However here you would also need to give some argument, as to why this kind of reasoning could not be applied to this case.
I could understand a community getting behind the construction of a water pipe, a place of worship (or even an operating system for personal computers). However a city wall is a slightly different kind of entity - this one is defining the boundaries of authority, it's a kind of us versus them entity.