Thank you for reporting a bug to Unity.
After reviewing the behavior, we've confirmed it aligns with the current design and intended use of the feature. We understand this may differ from your expectations or workflow. In this particular case, it is expected to see multiple draw calls because the different effects have to be sorted with respect to the camera, therefore the batching has to break to follow the correct order.
We will close this case as 'As Designed.' If you have feedback on how the feature could better meet your needs, please let us know - we value your input and consider it in future improvements.