I see the ruling as very, very clever, both economically and politically.
It curtails foreigners and outside investors who are intending to buy properties prior to getting PR, meaning the rental market and prices remain buoyant and consistent to support the market. It's likely intended to curb the current pace of new developments and avoid the risk of flooding the market with excess properties, especially so during a technical recession, which will drive down prices. The present economic climate is volatile and Singapore cannot risk instability in the real estate market - it attracts investors and is generally viewed as stable. It's a measure used to prevent price swings in the future.
Additionally, it flatters the Government at the same time by sending out a message to the people that they are trying to curb the number of foreigners here.
The downside is that it will make it very difficult for locals to buy property
as the prices will continue to rise, and the Singapore property market continues in it's bubblesque advancement.
In the bigger scheme of things it's actually a very wise move in order to prevent wild speculation and mass capital inflows given how the financial markets are swinging. The more capital that flows into a country, the more likely inflation is - Singapore doesn't need inflation at the moment. You may not see it as beneficial to individuals, but to prevent Singapore from getting hammered in the coming downturn, it's a smart policy.