We have sought clarification from NESA, and the answer is yes, it is still possible to do the mandatory 100 hours in Year 9 (or in Year 10).
NESA has advised that there are currently no changes to the mandatory requirements with the implementation of the new syllabuses. The mandatory requirement can be taught anywhere between Years 7 to 10, but preferably in Stage 4. (Reference: https://ace.nesa.nsw.edu.au/ace-4007)