Good question! Some qualifications have their transition period extended due to many different circumstances, but at its core, it’s to ensure that students and RTOs aren’t disadvantaged due to time restraints. For example, right now there are quite a lot of qualifications that have been granted transition period extensions due to the COVID crisis. ASQA has provided a webpage which outlines a lot of this information, including the specific products which have been extended (see https://www.asqa.gov.au/rto/change-scope/transition-items#extended-transition-periods)
Other reasons might include when an entire training package is updated (e.g., the BSB Business Services Training Package), which means that there would be a lot of qualifications to update. Imagine if your RTO offered a heap of BSB qualifications, only to find you needed to update every one of your BSB qualifications!
Having the odd qualification updated here and there shouldn’t pose too many issues, and 12 months should be more than enough time to implement a transition strategy. The link I provided before does go into depth, which would make for some “light” reading.