It's a really interesting role.
Royals have a special cachet in the minds of those with mental health disorders, because of their innate "specialness' - a politician who was elected doesn't have the same mental triggers. For example, when the Queen and Prince Philip died, there was an uptick in issues with individuals who believed they were secret love children of one or both. And obviously for those who think they ARE the queen, or the rightful heir, the queen's death was a major trigger.
The only reference he ever made relating to H&M was fans coming in from abroad believing Meghan was secretly in love with them (possibly catfished etc). Obviously he isn't very specific about what he does/individual cases.
His work involves assessing for markers of actual risk of these individuals in terms of making and whether or not they're actively planning to carry out an attack. He has two decades of experience in dealing with such individuals. And he's just one member of the team.