I was looking at the video and all the people on site. It looked VERY expensive to me, even if they are all volunteers. It’s nard to imagine so many nobles had the money and there was so much skilled manpower around in the 12th and 13th centuries to build those castles.
Of course, those minor castles and large estates were nothing compared to the Catholic cathedral building going on at the time.
You were talking about pre-black death and pre-great famine when Europe had a large population.
You could also use under age labor and you could work both people and animals more hours per day.
Not to mention these people would have been accustomed to this type of work to the point it would be second nature. And no tourists to have to stop and explain things to. :)