Nope, slower trains are not required to have streamlined
shapes.
Based on my Japanese study of trains (which is the producer, but
may not be the system here), our trains are considered High
Commuter Rate Electric Trains (通勤电車) (what a peace that Chinese and
Jap is accepted, easier from today on!), but in Japan no
通勤电車 are designed in such
a way in ours; heavy weight and low speed. All of those commuter
trains in Japan at least have 24(T)-32(M) tons only, and has
100km/h onwards speed. 80km/h is the junk speed made up by SMRT; I
have confidence our system can support 100km/h on stretches like
YCK to Khatib. We have few/none curves which are in R=300 so 70km/h
through curves is possible.
In Japan, if our trains are used, they are considered 近郊形
(Suburban type) trains, which is between express and commuter
types.
In Germany the Siemens, arggh, I won't know, but I feel that the
design for the Siemens and first batch Kawasaki/Tokyu Car
Corp/Kinki Car (Now Kinki Sharyo) (近畿車輛) made trainsets are
identical if not the same, and may be based on the same bluprint
just that electonics are different. And its also the difference in
electronics that give the Siemens its loud acceleration sounds.