Yes, this is the JSON format for account creation from the REST API.
Reference from the topic: Create account API | Delimited source | multi valued attribute - #4 by pattabhi
Here, you can observe that this scenario is possible from the API alone, but not from aggregation, because each value needs to be surrounded by double quotes.
"[email protected]","[email protected]","[email protected]"
If you mention it in the source file, it will not accept multiple values. Therefore, it is only possible via the API call.