This is not what you think. Some listings you saw on propertyguru websites are duplicate listings, meaning the same unit is being marketed by several agents. Thus explain the huge number of listings.
For some sellers, they are investors and would like to cash out their properties. Furthermore, those near TOP projects usually attract alot attention, thus many units are transacted near or just after TOP.
Hope I give you a good explanation.
If you are keen to get a unit there, do call me at 96836230. Like many agents, I also have a number of units there.