That’s where the older boys will be housed instead of out in a garden shed like their last abode.You only have to look at the top floor video tour to see the carpets, rooms etc haven't been touched there. The carpet colour and design is what you'd expect buying an old house thst hasn't been updated a while where her room is very different (still wallpaper but clear its been painted over). The skirting is even different in there. They may have left some areas untouched like the top floor but I suspect the main areas will have had some sort of general refurbishment.
The top floor tour I suspect is an area that wont be used generally for day to day living and isnt essential which is why its not been touched (as well as being inaccessible to some extent given the ladders) and maybe unusable lift (or maybe working but she didn't want to show it).