".....initial premise..flawed.."?
i admit that my learning is way below yours jack[and most posters here]but it seems to me that if an octopus is mostly soft, that there has to be some explanation if it gets fossilized.
rapid burial in sediment-, or some other process in longer time for which no doubt you have an explanation for.
i may well hold to the first but i am interested in what the alternative theory is ,if i can understand it. best wishes.