A list of about five things.
No buoyancy, it floats like the slab of wood it's made from, does not support a human body in the water.
Doesn't paddle like a modern board you have to swim it out to the line up and then swim it onto the wave.
Your swimming speed has to be wave catching speed.
No fins, most of us are used to the hold and direction drive fins give, not many at this stage are capable of using a set rail to ride across the face of the wave.
The linear speed of the boards is exceptional, but a shock on your first few waves and it is a constant battle to be able to stop the side slide and go across the face and be able to control release.
They are great learning boards and the Paipo size ones are way beyond ordinary body boards for sheer speed, an Alaia for me is fine but the rider is not capable
