the point is that part of the book value growth is because of this possible overpricing. if the correction comes their long term results will not look so rosy. i find accounting for real estate outside the US to be really idiotic.
for example in finland we just got REITs here. the first one (that went public) keeps revaluing their properties, shows this as profit and pays for a dividend by selling the (overvalued in books) apartments for an accounting loss.
as long as they sell considerably less than they have, the ones that are getting their "values" bumped will more than make it look like a profitable business. meanwhile, people are going crazy over easy ways to invest in real estate, and of course dividend yields

i'm not sure this is the case in HK, but when i looked at some of these i read that they value the properties to market and show this as profit. didn't check up on it, as it seems to be the case in most places.