They don't have to have watched StarWars or played fortnite to talk about and act out those things in the playground.
Only 2 children in my 7 year old's class of 7 and 8 year olds are allowed to play fortnight, although a few more (like my 7 year old) have seen older siblings play it. That doesn't stop all the boys in the class "playing fortnite" in the playground as a running about pretending game.
Star wars is the same - my 7 year old has actually watched it, but he plays starters with kids who's entire knowledge of StarWars comes from Lego StarWars or just from. Playground talk.
Mine does play Minecraft and talk about it, and has read some of the books.
At the same age my older DS only played football solidly at each and every opportunity, pretty much nothing else, but they're very different and also birth order makes a huge difference to what they're aware of.
Current 7 year old doesn't like or play football but will role out second hand football stories he's heard his brother tell if he feels the situation demands a football story.
At home he does watch too much TV but often prefers programmes which his friends don't watch (or don't admit watching) so doesn't talk about them with friends. He also tells ling rapid stream of consciousness annecdotes about butterflies he once watched or trees he sat in, and goes off into flights of fancy.
He "works out" with a pull up bar and does sit ups and press ups when restless, he is quite sporty and can't stay still but not a team sports player.
He plays Ninja Games which he acts out to a story inside his own head.
A lot of what 7 year olds talk about to one another is pack identity and fitting in, they don't necessarily spend their time alone at home doing the things that they talk about at school.