First thing to remember is that 200m hurdles for Athletics NSW is 10 flights, compared to 200m hurdles for Little Athletics which is only 5 flights ... so the times are not directly comparable.
Now, for All Schools in December 2021, the
rules explicitly forbid 12yo (born 2009) athletes from entering the 14yo (U15, born 2007) 200m hurdles.
1.6 Athletes in the 12 & 13 year age groups must not compete in the following events: 5000m, 200m hurdles (13yrs exempt), 400m hurdles, steeplechase, 5000m walk
However, for the 2022 Nationals, you will actually be U14 age group (turning 13yo in 2022), so that wouldn't apply anyway - and I'm not sure what the entry requirements will be.
So you won't be able to use All Schools to qualify for Nationals in 200m hurdles because you won't be allowed to compete. However, you should be allowed to enter the U15 200m hurdles at NSW Juniors in 2022 and use that as qualifying for 2022 Nationals - either based on time, or if you come in the top 3 and thus gain automatic qualifying.