That isn’t the case. The theme (see quote below) was designed for vBulletin 3.x
Most of these problems are just from lack of testing and tweaking the code to make it look right. Out of the box solutions like this often require almost as much work and testing as just doing it from scratch.
Instead of beating TPTB over the head about every single little oddity in this theme, my vote is to coax (goad?) them into making the “SDMB Classic” theme available to those who would prefer to use it. That requires very little coding or testing.