As for the case of service 83, notice that the road (Punggol
Central) will be further extended beyond the current U-turn point.
So LTA built a bus stop each on both side of the road, also Punggol
station is the only station in which the concourse is divided into
two by the road, so this mean passengers can board and alight at
any one of the two stops depending on which part of the concourse
they are going to/coming from. So SBST let service 83 to stop at
the bus stops on both sides of the road for the convenience of
passengers.
As for most other services, the 2 bus stops on both sides of the
road are used also by other services, so SBST/Tibs let the
particular loop service to stop on both side of the road for
passengers transferring to/from other services.