It probably all starts from a grain (sorry) of truth somewhere along the line - the whole Panatomic stuff came from New55 getting a batch of Shanghai made, then essentially stating it was 'like' the Panatomic-X variant used in Polaroid's Type 55 (which according to Bob Shanebrook shared a moniker with Panatomic-X, but had diverged massively for optimal performance with the Polaroid pods). If the Shanghai film does have any similarities to Kodak emulsions, it's more likely to be to pre-mid 50's ones - as opposed to 70's/80's ones of popular nostalgia. Anyone willing to put a sample of Shanghai though an electron microscope & see if it's polydisperse or of a more modern grain construction?
