Why the sudden tweak of the SSD from 4 years to 3 years?

This is my opinion – when the year 2020 comes, the property supply will actually reach the lowest point.

Those who purchased in 2016 will be able to sell in 2020. (4-year SSD).

While those who purchased in 2017, will be able to sell in 2020. (3-year SSD)

And the main reason why the SSD was tweaked was to ensure that the supply of units eligible for sale (without SSD) would be increased – instead of the possible 6,315 units available.