I have had dogs all my life and I currently have four dogs, I can honestly say I'm not aware of any of them ever smelling like biscuits. They have come home smelling of all sorts of country-side delights but never biscuits.
Awww, yes! My old labrador (sadly gone to doglet heaven) - his feet used to smell of biscuits I swear they did ! My cat's feet do too....weird....even weirder that I have smelt their paws ! !
perhaps they smell of whatever they are dreaming about, a bit like a chamaeleon only bigger and not so colouful and chamaeleons probably don't dream of biscuits.