You're right, and exporting the ticket will still flag the target as Vulnerable (but not generate a new Ticket for it), until the ticket is managed/closed (Marked "Complete", then "Acknowledged" by an administrator).
For example... you find Vulnerabilty "Bad Stuff" on your Weekly Scan "Boo" on May 3rd. Ticket 123 is generated.
On May 5th you export Ticket 123
Boo runs on May 10th, and you still see Bad Stuff, but you don't get a new Ticket.
Bob the Lazy network dude tells the Administrator that he's solved the Bad Stuff on May 11th, and Administrator (being on top of it) marks the ticket as "Complete" / "Acknowledged" that same day.
But the scan runs again on the 17th, only to notice that Bob lied = so he gets a new ticket to deal with!!
If Admin was lazy too, and left the ticket as complete but not Acknowledged - no new ticket would have been generated on the 17th. The "Acknowledged" is the key here.
I hope that helps!