I swear that battle royales are specifically designed for precisely timed dopamine release to make players have longer play sessions and to encourage addiction

You're really just describing live service games though, of which most battle royale games that come out in the modern era are a part of. Pretty much any AAA online multiplayer game is going to be about encouraging addiction and dopamine release. I think why battle royale games seem to be at the forefront of this is because they are inherently online multiplayer games. You couldn't really make a true "battle royale" game before the prevalence of online multiplayer without some major concessions.

Battle royale games happened to be the industry darling back in 2017 which is why so many AAA studios rushed to carve live service models out of them. If you pay close attention in the coming years you may notice that this will likely again happen to whatever new burgeoning genre takes the industry by storm. They already did it back in the early 2000s with MMO's.