Overhead is also calculated on number of control systems. So there are no benfit from having control systems that close with regards to overheads.The goal is likely to avoid too much of an overhead, as with the overhead calculations that everyone BUT ALD is currently subjected to, two full cycles of expansions (this one being the first) will push the Alliance's overhead above its income.
Since no one but Frontier knows what ALD's overhead calculation is, and indeed if it'll even be applied to anyone else, the prudent move is to move forward as if nothing has changed in terms of overhead calculations.