In the section A.1 Introduction, the 4th bullet point re: "How does the data get sent" describes 3 bulk data collection mechanisms: HTTP Bulk Data Collection, MQTT Bulk Data Collection, and USPEventNotif Bulk Data Collection.
Then goes on to say:
- From a data encoding perspective, both Bulk Data collection mechanisms support the CSV and JSON options as described later.
- From a data formatting perspective, both Bulk Data collection mechanisms support the Object Hierarchy and Name Value Pair report formats, also described later.
It's unclear if that is meant to refer to only 2 of the 3 mechanisms, and if so, which ones.
Link: https://usp.technology/specification/#sec:bulk-data-collection