While creating / updaing system Topic No effect of --identity systemassigned or --mi-system-assigned

### Describe the bug

While creating system topic no effect of --identity systemassigned or --mi-system-assigned

Object (principal) ID is not getting created.

### Related command

az eventgrid system-topic create --resource-group some-rg --location centralus --name some-topic --topic-type Microsoft.Storage.StorageAccounts --source /subscriptions/id/resourceGroups/some-rg/providers/Microsoft.Storage/storageAccounts/somesa --identity systemassigned

az eventgrid system-topic update --resource-group some-rg --name some-topic --identity systemassigned

az eventgrid system-topic update --resource-group some-rg --name some-topic --mi-system-assigned

### Errors

No Errors and at the same time **Object (principal) ID** is not getting created

### Issue script & Debug output

No Errors and at the same time **Object (principal) ID** is not getting created

### Expected behavior

**Object (principal) ID** should be created

### Environment Summary

az --version
azure-cli 2.45.0 *

core 2.45.0 *
telemetry 1.0.8 *

Extensions:
application-insights 0.1.19
containerapp 0.3.37

Dependencies:
msal 1.20.0
azure-mgmt-resource 21.1.0b1

### Additional context

N/A