As far as I know, beeing a WCHS-pax, special needs passangers are never asked for VDB.

(Once I was checking-in at FRA for an obersold flight and I saw the information sheets of VDB on the counter, but I wasn't given one.)

Sorry I forgot the source but this experience at FRA proofed my knowledge.

--quote--
* Print out the booking if you can and note that the word 'Confirmed' or 'HK' appear's next to the passenger's name
--unquote--

See if you can find the booking status "TK". TK is used when a confirmed booking (former "HK") got a time change and after pax is informed. And I know for sure that QR uses this code!