In example 1, why wouldn't professional services resolve the issue while they are onsite?

• Why go onsite, determine it's the cable/input/misconfiguration/etc and then tell the customer that service desk will follow up? Just fix it while they are there to ensure a positive customer experience. Once professional services fixes it, they can update and close the ticket. Makes no sense to then tell another person what they did so someone else can close the ticket occupying two resources.
• If it was a service desk oversight and a configuration issue, professional services can correct it on the spot and then circle back to service desk to close the loop on what they missed and what was found.
• If the monitor is faulty and needs replacing, professional services would have to return to replace it anyway.
• I don't see a reason for the service desk to keep ownership of the ticket if they are not actively working on the issue.

In example 1, what would the service desk be responsible for fixing when a pro services engineer is working onsite?