First, we’re taking that claimat face value, second, i imagine, he may have wanted to keep it secret so that one, if anyone wanted similar structure they have to get him to do the job or two, he didn’t want anyone else to steal his thunder.
> Thirdly, it should be pretty straightforward in 2018 to work out the details of a design from 1418.
If we could disassemble it perhaps. But destroying priceless and unique historical monuments just to find out how they were put together is frowned upon for some reason.
Would it? I would assume that it wouldn't warrant a news story in that case. Our ancestors were only a few levels lower on the tech tree; "it must be simple" doesn't follow from that.