So, as I understand it, and I don't, 5D is just fancy marketing due to the really weird properties of the crystals used to store the data in. They are just calling properties of the crystal, dimensions.

I found the wiki page on it https://en.wikipedia.org/wiki/5D_optical_data_storage

According to the University of Southampton:

The 5-dimensional discs [have] tiny patterns printed on 3 layers within the discs. Depending on the angle they are viewed from, these patterns can look completely different. This may sound like science fiction, but it's basically a really fancy optical illusion. In this case, the 5 dimensions inside of the discs are the size and orientation in relation to the 3-dimensional position of the nanostructures. The concept of being 5-dimensional means that one disc has several different images depending on the angle that one views it from, and the magnification of the microscope used to view it. Basically, each disc has multiple layers of micro and macro level images.[16]