If they are part of the federation, the Ba'ul would be who the Federation deal with (and Philipa acknowledges them when she rescues Saru) they would have told the federation that the Kelpians had an 'expiration' date and were showing mercy to the Kelpians. Remember Saru thought he was dying for sure and it was either through the Ba'ul where it was supposed to be painful or if they stayed on the planet would die in agony. So it's very much in line with Half a Life.
I guess one of those altruistic captains we see all the time on the shows that question the status quo and even deny federation citizens life-saving drugs to save some hippies from being moved to another planet, just didn't happen to be around then.