More Part 61 BS showing that you can't get a straight answer from those who are meant to know
Do I have to do training AND a flight review to fly certain types of aircraft?
Yes. Before flying these types of aircraft, you must complete initial training and a flight review on that type. Once you have completed the training and flight review, the aircraft type is covered by the flight review requirements for the class rating.
For example, the BE90/200 (Beechcraft King Air) is included in the multi-engine aeroplane class, but before flying it you need to complete BE90/200-specific training and a BE90/200 flight review. You can continue to fly the BE90/200 like all other types of aircraft in the multi-engine aeroplane class by completing a multi-engine aeroplane flight review.
Other types of aircraft covered by these requirements include: Cessna Caravan (C-208); PA31T; SA226-T Merlin IIIB; R22; R44; R66; Bell 206; Eurocopter EC120 and Hughes 500.
Remember - you still need to consider the general competency rule: do not fly an aircraft unless you are sure you are competent to do so.
https://www.casa.gov.au/standard-page/flight-reviews
Don't suppose you've already done "training and a flight review" on the 90 already? If so, the 200 and 90 being class rated aircraft means current in one, current in the other.
However, my reading of the document where it states "90/200 (King Air)" seems to imply that they are considered the same.
Go back to them and ask for further clarification. Or just go to the bloke that said your good to go and get that in writing from him!