To me a flashback is a flashback. (Or foreword or sideways), a super is just a way to indicate info presented to the audience, ideally info that is either vital to provide so as to avoid confusion, or info that is important to give gravity to a situation in the story.
It COULD in fact be dates/location that indicate when and where a flashback happens, or dates and location that alert us to a date and location of perhaps historical significance where the story begins, but the slug or action line flashback indication should suffice, and the conveying of the place and time might be by some considered more of the maker of the films job to create.
If a scene started in a desert or on an ocean or for example at a distance from or to something that the audience should know to help the story.. ( "Which desert is he in, many look the same?" - "What ocean is the ship in a storm upon, I can’t tell?” - “Damn and he was only 2 miles outside of town when he collapsed, what a shame!” - “Oh man, the hero only has 26 minutes left before the bomb will detonate!” -- "This scene started in the country, and a horse drawn carrige just passed by, where the hell am I, and at what specific year or period or era is it?")… then a super can be just the ticket, but still (As VP says), some will say it doesn’t belong at all, others will disagree.
I try to use it when it does something useful that there might be no other way to do.
-Thanks-