(1) Haven't heard that "woo". Let me ask my friend "sin". 8)
(2) I think the size (gross) won't have different. Otherwise void the contract (unless already stated). Net may be a little bit larger at high level as the wall can be thinner. The difference should be the floor plan. Remembered when I bought RC Hutchison said they can help to partition the flat as 4 rooms free of charge (only valid if requested at the time of signing the rovisional contract) They may offer some other different plans for buyer.