This seems disingenuous to me, since most sites have undergone multiple phases of conservation work in order to gain their current appearance. Historic sites are often eager to describe "historic" changes to the building, but are less inclined to discuss the staff repainting the room to a more "appropriate" color in the 1980s. I think it's time for historic sites to be more transparent about their preservation choices and to incorporate education on preservation into their interpretive plans when appropriate.
Following are sites we visited and observations about their preservation choices, plus questions to consider related to the interpretation of preservation at historic sites.
Ever seen Brideshead Revisited? Both the mini series and the movie were filmed in this opulent mansion. It's a hodgepodge of architectural styles built over 100 years- from English Baroque to Palladian to Georgian, all visible in the facade! The owners still live in the house and they decide to update the house as they see fit. They reupholster their antique furniture in bright blue, have murals painted in the style that they think the house's architect would have approved, and allowed a digital wallpaper of dark, Catholic themed murals a la Inquisition to be plastered in a room, even though the family is not and never has been Catholic. I was able to figure out that these alterations were not historic, but would most visitors know to ask? What length should a site go to in order to inform their visitors to what is a modern alteration?
Castle Howard: http://www.castlehoward.co.uk/
Treasurer's House: http://www.nationaltrust.org.uk/main/w-treasurershouseyork
Whitby Abbey, http://www.english-heritage.org.uk/daysout/properties/whitby-abbey/