I'd be tempted to ask the CII direct about that
Below taken from above link for AF8 coursework FAQs, page 6. Would suggest your thinking is correct, but as Andy said probably worth double checking with CII.
What are the timescales and deadlines involved?
Your enrolment lasts for 12 months and all assignments, including any re-submissions necessary, should be submitted within that time.
▪ Assignment 1 – this needs to be submitted within 3 months of your enrolment
▪ Assignment 2 – this needs to be submitted within 6 months of your enrolment
▪ Assignment 3 – this needs to be submitted within 9 months of your enrolment
**▪ Any re-submissions – these need to be submitted within 12 months of your enrolment
You can find your actual assignment deadlines for your unit in your RevisionMate course, as well as the email you receive upon enrolment. These deadlines are final, and we encourage you to submit before the dates to ensure you complete the course on time.
If you miss an assignment deadline you will automatically receive a 'timed out' notification. You will need to purchase a re-submission to continue with the course. If you fail to complete and pass all three assignments (including any re-submissions necessary) within 12 months of enrolment, your enrolment will end, and your CII exam record will be updated to include either a 'Fail' or 'Timed out' for the unit.