Issue has been submitted upstream to Seldon project here:

https://github.com/SeldonIO/seldon-core/issues/3963

The high level summary of the issue is that when you deploy Seldon as a namespace scoped operator (like ODH does) the pod for the first instance of the Seldon Operator this is deployed is the pod that will manage all SeldonDeployment resources no matter what namespace it is located in.