what type of time travel is this?
we could rule out the time travel where they were missing since the 80s
but we can also rule out the future self of Jennifer not remembering her trip and not be waiting for her or avoiding her? so an alternate timeline where Marty never went to the future or never time traveled again but just went down his road of life but editing that future plays out in his timeline where he would have knowledge of having changed events once he returned had back to the future 3 events not happened? back to the future IV could just be how Marty's life is different