Yup, really. This almost sounded like an argument from incredulity. Which is precisely ruling it out by deduction. It was certainly not a conclusion arrived at via induction. The 'flatly not possible' was precisely the way scientists reacted to rogue waves. The phenomenon did not fit with current theory. It was deemed impossible and people were told they were imaging things because of emotions. It was presumed that it had to be like other waves - which come in batches. IOW it was decided that they knew that this phenomenon could not take place because what they considered similar phenomena could not possibly extend into this kind. This was deduction - with a lot of assumptions about what the phenomenon would have to be if it existed and none of these could exist. But then they did.