So, what's their point (get it......point!!!
).
The only time the universe would've had fewer dimensions would be right at the very start of the BB process....essentially it would have zero dimensions. The moment it started to expand, it would have to become an extremely small 3D (+ time) object. The reason being the smaller the number of dimensions, the fewer the number of process that occur which can drive the expansion along and produce what we see. Many processes won't occur at all, such as nuclear fusion etc. If the universe acted in the way they believe, we wouldn't be here today to discuss the matter...literally.