If you want to book online DRW-HVB or HVB-SYD and select Business it will only return award seats with the "i" indicating one sector is Y class. I tried for the last business sale ($1290 J return DRW-BNE) but you could not book online as a single journey through to HVB and confirmed tonight it seems to apply for some journeys where Y is only class available for one leg. Randomly checked DPO-SYD and the combined Y/J journey shows as an option. Most confusing. Perhaps someone can enlighten me on why some mandatory Y/J display and others don't.