That is not the reason. It is because as you build a RG in the editor and place the elements inside, you place only a single element which gets populated in all RG cells in run mode, so if have 100 results in the RG, the single element is then transformed into 100 different elements, one for each cell/result.
Because of this, Bubble doesn’t have a reference for which cell the element that is clicked is, so it only assumes it is to manipulate other elements within the same cell.
So making workflows that are triggered by elements outside of the RG, to execute in a specific cell is impossible without the help of a plugin, one of which is called Orchestra.
Put button in the RG. Put your confetti function outside the RG. For workflow of the button in the RG have it trigger the confetti function that is outside of the RG, so the confetti is on the page, not within an RG Cell.