surely the risks and technical principles are the same as a low hour guy flying a 320?
I'm not so sure. Having flown 320 and 330 (base-trainer and TRE) with very, very many new-to-type pilots I believe the 320 training simply gets them up to speed with the A/c with a bit of 'routes and airfields' thrown in.
The 330 is different. First, the aircraft is not a big 320 - far from it. Second, the 'routes and airfields' bit takes on a whole new dimension: Calgary at -35*C; Orlando TS in the summer (not to mention the airfield training traffic); Dom Rep ATC and approaches; Atlantic crossing procedures and CPDLC/ADS... I could go on.
Certainly have taken many pilots on their first-time crossing but they all had a few thousand hours. Who wants a 500 hrs pilot with both ratings?
The arrangement is unsound in my humble opinion.