It sounds like they developed the system, then tried to make it responsive. As if they started from scratch with no code reuse.
Wouldn't it be just a trifle better to find or develop the best responsive framework that they can and use it across most of their projects, fitting each one into the framework with whatever adjustments are needed?
That would also make maintenance easier as all their staff would know how that framework worked.
The same goes for the back end stuff - a company that big ought to have lots of existing general purpose code which can easily be tweaked to fit.
It's almost as if they handed the entire analysis and development process to completely inexperienced staff who had never worked on any other project for them and had no access to the code for their other projects or any advice from the experience gained in building them.
Since the entire point of using one of these firms rather than developing in-house is to take advantage of their existing experience in doing this kind of development this seems, shall we say, a trifle odd.