The cake was done by Tipsy Cakes in Chicago in Chicago. Perhaps they can give you some information.
The lines look piped on to me.
LOOKS LIKE BUTTERCREAM PIPED !
Afrosted with buttercream than textured with a spatuala. just spin the cake and use the spatula as a comb to create that effect.
ALooks similar to a corkscrew technique. Charm city cakes West posted a quick video tutorial on their instagram feed @charmcitycakeswest, exactly what eendy89 describes
Thank you all!