Ok fellas, the verdict is out. Spec Cs do not come with the sweep function from the factory, only the JDM STIs do. I managed to get the information on the 'sequential startup function' from the JDM owners' manual translated.
Heres what it says:
Initializing the Indicating needle
For red luminescent and white luminescent, upon turning the engine switch to "On", all 4 meter indicating needles will indicate the maximum and then immediately return.
(excluding STI spec C)
Setting Method
STI indicating needle can be set or deactivated using the method below.
1. When the engine switch is at "ON", and REV Indicator Setting **** is turned either to the right or left, setting or deactivating can be done by pushing the Trip Switch/Trip Meter Reset ****.
When this is done, the buzzer will sound and the external temperature display will change to the initial start-up display. The initial start-up mark and "ON", or "--" will be displayed.
Although the above information is taken from the owners' manual for the MY06-07 hawkeye JDM GDB STI. I believe the sweep function was not included in the earlier Spec Cs as well (MY03-05)
as confirmed by CannonFodder and TX.
So i guess the Spec Cs that have the sweep function were programmed in from new by the supplier (as confirmed possible by Robocop and Shaun) or was done by a previous owner.