We should probably take Metro's word for it.
Metro Boomin, one of the hottest, possibly retired, producers in the rap game, has unmistakably altered the sound of modern rap music in a major way. That being said, he doesn't feel as though he invented one of the sounds that he became infamous for: the prevalence of flute in modern rap production.
In an in-depth profile with High Snobiety, Metro's history with flute rap is laid out in detail. The genesis of the trend was Future's Hndrxx smash hit, "Mask Off," which was produced by Metro, and featured an infectious flute sample and an hook so catchy that it was impossible to ever fully get it out of your head. This resulted in a wave of internet memes where the flute sample was edited into different videos. Murda Beatz's production on Drake's "Portland" off his More Life mixtape(?), carried the torch and brought the trend even further.
Metro, however, disagrees that he should be given any credit for his flutes. "Hip-hop shit just like fashion shit. Shit just goes and comes back," said Metro. "I’m not going to say like I’m the n*gga that invented the flute. Growing up, flute riffs was big in rap back then. It’s what I listened to. It inspires you and influences you to bring that back around."
While it's true that Metro was far from the first producer to ever use a flute in his beats (listen to Jay Z's "Big Pimpin" for one early example), but he probably deserves some credit for influencing that particular moment in rap trends.