It makes sense if you cook pasta, for example: you want those noodles salty inside too. If you mash or blend, however, there's no such thing as inside or outside. As a result, I never salt water when I boil potatoes for mashing. If you salt afterwards, some of the salt won't go down the drain. One Gordon Ramsay, on the other hand, an experienced chef, made a point of salting boiling water when cooking his broccoli soup. He didn't explain his reasoning, let alone provide some peer-reviewed publications that would corroborate whatever point he had, but it made me thinking: could there, indeed, be good reasons for salting water if you mash or blend your vegetables?
No! It's not just about "adding salt to potato water". I respectfully urge you to reopen the question