Certainly, large programs are harder to maintain than small programs. Certainly, modularity and encapsulation helps, in any language. The implication that, therefore, choice of language is irrelevant to maintainability is spurious.
Definition of large program is "program, which is hard to maintain". So large programs are hard to maintain by definition.
You're referring to a line I never drew. Programs can be larger or smaller in many dimensions - LoC, complexity, features... Other things being equal, the smaller program is easier to deal with. We don't need to say "these programs are large and these are small" to make valid inferences in this area.