I assume that ONLY the SysEx components would be affected by the 'problem' of needing the SysEx ID.
JohnG: You are correct that the beginning of the messages all use a Manufacturer ID of hex 7E (Universal System Exclusive - Non-Real Time), but within the data of the "Discovery" and "Reply to Discovery" messages, there are fields for Manufacturer ID that represent the device that is initiating or replying to the discovery request:
Ideally it'd be best to pay for a Manufacturer ID assignment to ensure there won't be any conflicts if you ever need to define device-specific messages. But if you are a developer that only wants to query MIDI 2.0 devices, I wonder if there is any harm in putting a Manufacturer ID like hex 7D (Non-Commercial) or hex 7E (Universal System Exclusive - Non-Real Time) in the Discovery message? I don't understand all the details and potential use cases of MIDI 2.0 to know if this could cause a problem.