Noted, thanks for doing the research. It did seem hard to believe.
I usually read 2 or 3 UK papers a day and watch several Brit YouTubers ( these are NOT gossip mongers and KNOW what they are talking about; one being an Aristo ) as well.
Since I had ONLY read parts of one today, I checked the others.
First of all, NO ROYAL is permitted to sell a CROWN PROPERTY! And a DUTCHY is CROWN PROPERTY! The CAN be "gifted"/come into possession by the next heir to the throne. That's IT!
The personally owned property, such as Osborne Island, which Prince Albert bought for Queen Victoria, as a get-a-away place, is one such.