My apologies, I really didn't word that very well.

If you take my UK issued IDL, I have A thru E stamped, so in theory, that would indicate I'm licensed to drive anything from a motorcycle 'A' to an HGV 'E' category vehicle.

In reality, per my UK Driving License, I'm only permitted to drive a vehicle in a sub category of 'E'. Like Sanosuke 'A' is stamped as I'm allowed to ride a scooter, even though I didn't renew the motorcycle bit (for my own protection ) of my UK license, .

As you've all pointed out, vehicle categories are present and what I really should have just said was; that an IDL is non restrictive in that the categories are vague and don't tell the whole truth without your regular license.