I disagree with that , if you have already done biometric , while filling out the PR and go to submit the Fee at that time they normally ask you and if you have already done biometric or not . If you answer Yes then they will not ask you to do it again.
Their system is advance now , my mom and dad provided biometric for PR application and after the bio metric was done i saw the Biometric was automatically updated for Super visa application as well. So as long as you have biometric in their system it should be able to connect to existing in process application i believe. both of my application was under different user ID and they are 2 separate account. I was surprise to see how they got connect to Super Visa application, i didn't expect that , i thought i will have to send a web form to let them know about biometric and update their record for super visa so i wont have to pay fee again .