On single nozzle Mini, if Nozzle Switch Retraction Distance is not set to zero, retraction occurs during print startup
Cura 3.6.8, Win 10, Intel quad core, single nozzle Mini:
If Nozzle Switch Retraction Distance is not set to zero, retraction occurs, apparently as part of the nozzle wiping routine.
In my case, the stock material settings for the material I'm using have this set to 16 mm, so the filament retracted nearly all the way during startup, and thus there was no filament in the nozzle when the print began.