Perhaps this curiosity might be explained because Castagna did a lot of work on Isottas, whereas Touring seemed to favor Alfa Romeo and few or none of its Isotta Fraschinis survive. My personal library has almost nothing dealing with Isotta Fraschini, so I hope readers can provide the needed information.
In the years around 1930, Isotta Fraschinis were powered by inline eight cylinder motors that required fairly long hoods. However, hoods seen on these cars seem longer than necessary to house such engines. Regardless, the proportions created by factory hoods made it easier for coachbuilders (who provided all Isotta bodies in those days) to create impressive designs.
Below are images of Isottas with Touring bodies.