London Terminals to Zones 1-6 One-Day Travelcard printed e-ticket

I found a passenger at my local suburban London Underground station stuck at the ticket gates, trying to scan a barcode on an A4 sheet of paper. The gateline staff member had briefly left the gateline unattended. I spoke to the passenger, a foreign tourist, and found he had a London Terminals to Zones 1-6 One-Day Travelcard as a printed e-ticket. I was well out of my depth and called the staff member from the supervisor's office!
But so was the staff member who tried to tell the passenger that he had only a booking confirmation and therefore needed to collect his actual ticket from a National Rail station, until I pointed out that it was headed "This is your travel ticket".
Is it common to see this ticket in this format? Should it have been issued like this? I'm kicking myself that I didn't note what retailer had sold it.

That sounds like an issuing error to me - unless you can trade it in for a gate pass at a mainline ticket office like you used to be able to with SPORTIS issued Travelcards?

First time I've heard of a Travelcard being issued in that format, though we did have a brief period where a certain online retailer was issuing tickets involving cross-London transfers as barcode tickets, which London Underground refused to accept; and around the same time they decided to unilaterally create a new ticket type for certain flows at completely the wrong price, which TVMs and Desktop TIS were unable to issue.

Both situations were handled as retailing errors, with new tickets being issued and charged back to the original retailer.