I did note this, and another poster said its completely normal,...

I did note this, and another poster said its completely normal, there are "at least 20 office spaces on the floor" although it "could be more, could be less"
Thus lots of leases available, and not necessarily that CGB's office is untenanted.

After some further quick googling, i have found a map of the building.
There appear to be 44 individual office spaces (give or take a couple, i did scan with my aging eyes and not tick off each office to be 100% sure)




The rentals ive seen starting at $3600 a month, seem to be very prestigious compared to a quick google of other city offerings.

https://www.realcommercial.com.au/short-term-workspace/castlereagh-street/serviced-office-space5633


https://clarenceprofessionalgroup.com.au/serviced-offices/133-castlereagh-street/