Hi,
We double-checked and security hotspot status are actually synchronized between branches:
We will update the documentation.
Regarding your initial problem where the synchronization did not happen, it might be caused by multiple factors. One common case where issue sync between branches is not working is when files have been renamed.
Another case could be multiple levels of branch “forking”. Like master → branchA → branchB.
If you can reproduce it again, feel free to re-open a thread, and we can try to investigate.