That is true.
"Unemotional" may be the wrong term to describe Singaporeans in general. It really impossible for any person alive to be unemotional.
Rather, one have to see it as the mental state and intellectual disposition of a people as a whole reacting, mostly unconsciously, to the social environment, according to its nature. In other words they are a product of the environment they exist in. And it manifests as plainly discernible emotions of an underlying unhappiness which they display.
If anything, the more sensitive may even perceive it as a passive and resigned attitude with undertones of seething anger underneath.
If you have given almost 50 years of uninterrupted endorsement to a government who treat others especially foreigners better than they treat you and you are just a mere statistic in a total they call the economy, how not to be unhappy? Singaporeans' unemotional trait saves us from crying out loud.