Good point, re soft bodies fossilizing more rarely - because what may have happened is the squids just didn't show up in the fossil record for a very long time,

Good point, re soft bodies fossilizing more rarely - because what may have happened is the squids just didn't show up in the fossil record for a very long time, nor the proto-squids. Ocean acidification at various periods (say due to CO2 variations at different periods, which were large) would be a factor. I'm not saying the 33 scientists weren't well aware of these considerations, though.