As write in the Game packaging guidelines, the package should fit with "Package game files and data files separately, if possible, to reduce size of bugfix updates. This must be done if upstream packages game data in separate tarballs." But the current package is using a sub-package data and not a separate package, which is useless. So as upstream never provides bugfix release, the best is just to join the sub-package to the main one.
There is nothing to gain by making such a change after it has already been split. The guideline is more suited for new game packages being submitted, not for existing packages.