You answered your own question.
SE was about those shiny, obvious moments. The cliche gift and flowers and double dates, high school dances, a compelled ferris wheel ride in the middle of the night, saying “I Love You” too soon and too often. They’re about the idea of true love, the youthful idealistic version of a romance and of what it means to be in a reationship.
DE is about the reality of a relationship. Yes, they have big moments and beautiful speeches but they’re really more about the mundane, those little acts and silent understandings that just…happen. They’re about a rose plucked out of an arrangement and casually given, roadtrips taken at the drop of a hat, sudden and unexpected kisses while hiding out at a sketchy motel. They’re about making mistakes and saying the wrong thing or making bad choices but doing it out of love and out of necessity and being able to work your way back to each other afterwards. They’re about being there even when it’s hard and things aren’t all fairytales and pixie dust. They’re about showing their love for each other with simple, spontaneous actions more so than with words or big gestures.
SE happened in the big moments but DE was happening in all the little moments in between.
And so the reason that there are SE’rs who don’t understand what the writers did is because they were always just caught up in the obvious story, the sparkly upper layer. The real story was happening underneath the surface, quiet and hidden and unfolding slowly and that’s the one DE’rs have been watching all along.