I would think they at least had the foresight to shoot “clean” background plates during TFA just in case they revisited this later.
I think you mean TLJ? Actually that’s interesting to consider. Back when Trevorrow was on IX he had Rian Johnson shoot a scene for IX while filming TLJ because it logistically made sense to do so. Never thought about it but definitely could have been an additional part of that flashback. Obviously no way to know at this point if that scene (whatever it actually is) will be used in JJ’s IX.
Didn’t we see first see the burning Jedi temple in Rey’s vision in TFA?
Reminds me how they wanted to shoot all the Dagobah scenes for ROTJ during production on Empire, but ran out of time. Lucas shot two scenes for ROTS while making AOTC, but neither got used.