I am using Azure App service plan to host web App which process Service Bus Topic message.
I am using Azure Function App also which has http trigger to execute Event grid data.
Both Web App(App Service Plan) and Function App(Elastic Premium plan) have staging slots in production.

At the time of swapping slot I observed stgaing slot for web app is processing message. Is this expected behaviour?
For function app staging slot, I am not observing this behaviour. Why so ?