Does providing further information restart the assessment timeframe?

The assessment clock continues from where it stopped; it does not go back to day one.

For example, if 15 working days of the applicable assessment timeframe have already passed when ACT Planning issues a further information request, the assessment timeframe pauses. Once you provide the requested information, the clock recommences rather than starting again from zero.

There is an important distinction if you change the proposal when responding. ACT Planning says you should provide only the information requested. If you change the application or provide additional information beyond what was requested, you may need to lodge a DA amendment, and an amendment restarts the DA timeframe.

Reference: ACT Planning – After you apply  - Approval timeframes - https://www.planning.act.gov.au/applications-and-assessments/development-applications/after-you-apply