My parents are currently traveling in Europe and had the following 4 LH flights booked on a single itinerary:

9/6 FRA - PRG refundable J
9/11 PRG - VIE refundable J
9/15 VIE - BUD refundable J
9/19 BUD - FRA refundable Z

They flew the 1st two legs, but cancelled the VIE - BUD leg on 9/13. They will fly the BUD - FRA leg in a few days. They're being told there's no refund for the unused VIE - BUD leg, despite it being a refundable fare. Is this accurate?