The request is disproportionate IMO. However Optus seems to have recently ticked up with their security ID questions. The standard three are seemingly no longer enough. Licence ID is just one of many items Optus has about you in their ID database.
FWIW you could provide the info but just change a number. If its a legit check against something they already know then they'll tell you it was incorrect. If its something else they'll just say thankyou and proceed.
@Nome68, driver’s license seems like a little much.
We might request further information if we feel as if there might be a security concern.
Which service channel did you go through? For example, live chat, over the phone etc.
Regarding driving license number. This is due to Optus has introduced a new system which only proceeds with orders when a credit check is completed. For credit check completion certain information has to be added which cannot be retrieved or updated without the Account holder's permission, hence advisors are asking for the details.
All the calls which are made to and made by Optus are recorded there is no chance of misusing your information.