That is an old post, and the information shared is totally wrong
It IS a country-wide legality issue in Singapore. You are not allowed to rent any properties lesser than a period less than 6 months. The law states when signing a lease, you need a minimum 6 months lease. But airbnb try to play with the rules saying Singapore never stated you can't rent lesser than 6 months, only that you have to rent more than 6 months. But currently, a new law has come into effect making airbnb illegal.
And those with rent out their place are usually tenants and not actual owners. They do so too even when they knew it was illegal. That is because Singapore rules punishes the actual house owners instead of the ones who rents them out illegally. They know they can get off scot-free when caught, and just run off with the money.