I'd have to double check with my G3 iBook, but I'm pretty sure it has one. I know for a fact my G4 iBooks which look almost identical have them.
Are you sure the computer is actually going to sleep? Try a clean install or boot it from another drive (like TDM)?
None of the PPC Macs I have activate the light when the display turns off (with the computer still awake), unlike my Intel Macs. For example, on my Intel Macs, the light would turn on when I put the computer to sleep, and would start pulsing after a while (when it actually goes to sleep), whereas on my PPC Macs it jumps directly to pulsing only after it fully goes to sleep, so could it be that your machine does not actually ever go to full sleep?
I'll check later on my computer if you need me to.
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