That paper was published in 2019 and also discusses a previous campaign so is before the 2024 advert so it doesn't say anything about it.
I included it because it's worth reading for the evidence and discussion to flesh out the final line in the abstract I quoted.
Our findings show clearly that anyone who wants to intervene can safely do so. Last-minute intervention requires no specific learning and can be highly effective when spontaneous and unscripted. In 2018, Network Rail in partnership with Samaritans launched a campaign entitled ‘Small Talk Saves Lives’, encouraging rail travellers simply to say ‘Hello’ and strike up a normal conversation if they are concerned about someone.28 Our data confirm that this campaign message is entirely appropriate as far as the initial approach to a vulnerable person is concerned. However, it fails to recognise the intense, prolonged and taxing nature of intervention, the complex juggling acts that interveners may have to perform in the course of trying to keep someone safe, and the troubling emotions they may be left with. It is no small thing to save a life. The conundrum for public education is how to prepare people adequately for the challenges they may face without deterring them from intervening.
I'd think it might be worth reading and considering by people interested in the topic. That's separate to the current advert.
Molko's experience is a scenario that is very similar to the discussions in that paper.
It was enough to reset my frame of mind a bit and I didn’t end up doing it, it obviously didn’t solve anything long term but in that moment where my thinking was unclear it brought me back to reality enough that I was able to get myself safely home.