Well I just tested this and although they are sent individually (HTTP upload now on 4.8.1282), you can select multiple files in the chest, see image.
Right click on the selected files and select email to Alwil software (hopefully this text will be changed in due course), whilst you only see one displayed you can enter the details (copy any general info that is the same for all) and click Submit.
Now the next one is in view (was behind the first), paste any general text and any additional comments and click Submit, do this for all and your good to go, much quicker than the old system.
Yes it would be nice if the Comma separator for multiple submissions (of the same type, Undetected/FP, etc.) as used in other avast areas could be used here.