I think the difference here isn't fresh vs frozen, but rather unprocessed vs processed.
Heston freezes solid whole pieces of potato, In-n-Out likely uses whole pieces of potato, seasoned. McDonald's likely mashes everything up, blends it all with preservatives and flavour enhancers and forms it into fry-shaped pieces.
Heston freezes solid whole pieces of potato, In-n-Out likely uses whole pieces of potato, seasoned. McDonald's likely mashes everything up, blends it all with preservatives and flavour enhancers and forms it into fry-shaped pieces.