well, the same goes for EMS, but it doesn't mean it's not a tracking number. If it shows pickup and delivery, then it's a tracking number. What you mean is that it's not real time traceable like UPS/Fedex.
The registered number is more like a delivery confirmation number in US. It shows the pickup, major hub and destination scan. It shows something and a few delaers give the number anyway.
Btw, the registered number always work for me. Usually, I ll receive the package in 2 days after it arrives JFK.