The intention of adding it (in my edit anyway) was to give the vision some more immediate relevance to Rey’s emotional state - she’s afraid of losing people forever and fears that this has just happened with Finn. I don’t think it needs to speak to the rest of the trilogy.
I see your point, but if her vision shows the past and future, such as accurately predicting her fight in the snowy woods with Kylo Ren, then this would be an event that never happened. It could work for a personal nightmare she’s having, but the vision is mainly triggered from touching the lightsaber which has had a legacy that she is unaware of and is experiencing and interacting with for her first time.
You could say that Kylo seeing Rey while standing with his knights in the rain never happened either. I don’t know, making one aspect of the vision be a more personal nightmare makes it more, well, personal than the rest of it and gives the rest of the vision some more grounding in an emotional reality.