Every since Coke changed Diet Coke with Lime into Diet Coke with Lime & Ginger (yuck), I get the plain Diet Coke and then add in a splash of Sprite.Freestyle works by mixing the primary (coke, diet coke, sprite, fanta etc) syrup with the secondary (vanilla, orange, cherry, lime etc) syrup. So the cherry flavour is likely different to proper Cherry Coke as the cherry syrup plus coke syrup is different to cherry coke syrup.
When using freestyle I like to mix, so part plain diet coke, part with cherry and part vanilla. adding some plain in stops it being too sweet.