Presumably it's savoury primarily in the sense of "pleasing to the taste; appetizing; agreeable" (OED).
For me, though, the first meaning of savoury is 'the opposite of sweet' - and as I would always expect a cheese bap to be savoury rather than sweet (without the need for it to be stated), the label made me do a double-take.
That probably says more about me than the bap, though.
