I see it more as a matter of the future scenes from Arrow being an extended backdoor pilot for GA&tC. After all, it's not like they ever had any real connection to the present-day Arrow narrative until Mia et al. were swept back to the present.
Well yeah, but I think it's enough that Mia remembers it. From an in-story perspective it works as an explanation for both her abilities and as motivation for her to take up the mantle, to prevent that sort of future ever becoming real, and it works from a viewer perspective, because we get to see how different characters turned out under different circumstances. But if suddenly every character gets woken up and remembers both version of themselves instead of spending time worldbuilding this new world you have main characters that are at best only half there and I just don't see any compelling reason to make it so.