Sort of he got the wizards to create round world which has no magic and worked with several scientists to make their observations correct. I know it is a few years ago as Terry has been dead for a while but I add a link below so you can see the premise. So yes there is fiction and true fact but it is easy enough to tell apart.
https://www.amazon.co.uk/Science-Discworld-Terry-Pratchett/dp/0091951704
There's a very good chapter in The Science of Discworld about this very subject:
anus, ivention of, page 231:
https://www.amazon.co.uk/Science-Discworld-Terry-Pratchett/dp/0091951704