VA disability Back Pay

I applied for a VA disability PTSD increase in December 2023, but it was denied in June 2024. I appealed the decision and submitted additional evidence, including a nexus letter, in July 2024. My increase was approved in late October 2024, and I received back pay for the period from July to October.

Shouldn’t I have received back pay from December 2023 (when I originally applied) through October 2024? Any advice or similar experiences would be appreciated!