Spacefolder ships use the Holtzman effect to bend spacetime. Computers were used to find safe routes before the Butlerian Jihad. Without computers, guild navigators use their prescience to find safe routes. Spice doesn’t allow spacetime bending, just navigating through bent spacetime without a high fatality rate from flying into stars.
It’s explicitly described as allowing spacetime bending in the books, maybe Villeneuve will talk more about it in the nexr movies
Spacefolder ships use the Holtzman effect to bend spacetime. Computers were used to find safe routes before the Butlerian Jihad. Without computers, guild navigators use their prescience to find safe routes. Spice doesn’t allow spacetime bending, just navigating through bent spacetime without a high fatality rate from flying into stars.