This is completely untrue. Some A330s are ex JQ birds which are pretty much the same seats as Y, just difference in service. Others have Skybeds and then there is, of course, the new product. The 738 has a standard hard product across the entire fleet.

You can generally tell which aircraft you are getting based on the seatmap.

To see what the morning A330 flight to MEL often is, as I have experience almost every fortnight, it is this cabin with the dreaded 'workspace' for the middle row. I prefer dual aisle aircraft so specifically book these flights.