I'm on 0302 and P3Dv4.5HF3
the DUAL BLEED light should came on when doing preflight-F/O.
Currently on CS733, it seems the DUAL BLEED light are only on when switches are on and engines and APU are running.

This light is tricky, it's logic is based on the Actually position of APU BLEED valve and ISOLATION valve, BUT the Switch position of ENG BLEED valve, so with APU running and APU BLEED ON, and engines cutoff but ENG BLEEDs ON as in preflight configuration, it should came lit. But even after  ENGINE satrted, if you Turn off the APU but without place the APU BLEED switches off, this light will extinguished as no APU air to keep APU bleed valve open .