The reason this act breaks a moral boundary is that it subverts a principle of "ends" [1]. A genuine random act of kindness cannot occur if it's being filmed. Filming the act turns it into a virtue display. It also turns the subject into an object of utility, a means and not and end in themself. [1] https://en.wikipedia.org/wiki/Kingdom_of_Ends
The issue here is how it plays out the person gifted isn’t more than a prop.