Well, that was weird. A quick Google search doesn't answer it directly but it might be something like:
FAA (and maybe EASA) takes it as 2 types but it only requires a difference training from the 330->350.
From the link: The new regulatory approval means that pilots who are qualified and current on the A330 can already commence their preparations to take the A350 XWB’s controls by undergoing “differences training” only
FAA (and maybe EASA) takes it as 2 types but it only requires a difference training from the 330->350.
From the link: The new regulatory approval means that pilots who are qualified and current on the A330 can already commence their preparations to take the A350 XWB’s controls by undergoing “differences training” only
Based on https://www.pprune.org/tech-log/609896-sff-a330-a350.html