Rey had zero idea who Anakin Skywalker was and seeing him in his young form is too out of left field for me, for him to appear I think he would need to show up before that moment for a Rey connection to work.
She says in TLJ that she knew about the redemption of Luke’s father… Also, Anakin literally speaks to her in TROS. There’s several other minor examples of her knowledge of Anakin but these are the main ones.
She also previously knew about the legend of Luke Skywalker but if she never shared a scene with him I would be feeling the same thing of who is this old man she’s looking at, if Anakin could be seen more than just heard when he helps I would find the whole thing less jarring, I understand he’s part of the family but his presence doesn’t feel organic.