Generally speaking, I am a big advocate of NOT touching things when you dive or snorkel. Just observe with your eyes and enjoy being present, you're not there to touch or disrupt; it's the whole point of appreciating and preserving nature. (I'm not referring to other activities which may have purpose, such as fishing; separate topic....)
And yes, sunscreen or whatever else can indeed be harmful, potentially. If I recall the first shot of the documentary where they come together, the shot appears as if they are both reaching toward each other simultaneously, as if there's a mutual curiosity. Who knows, maybe he'd been feeding her for some time before they took that shot

... a bit of training... but that's a cynical thought!
It can also be dangerous, as they may have discussed... I don't recall the past conversations, but I know that if an octo decides it wants to wrap its 8 arms around you and restrict your movement, you're going to have a bad time... especially if you're free-diving!!
Anyhow, that's my take...
