I’ve seen the same problem, and it would be great to get an acknowledgment here from the F-Stop team that they’re aware of it.
BTW, F-Stop isn’t the only app guilty of this – Samsung’s Gallry, QuickPick and others also, strangely, copy files instead of moving.
A nasty side-effect of updating the timestamps is that all videos will be sorted at the top (if you sort by date).
