I just think it would have been an easy thing for a manga of that era to do. A large part of FOTNS was Kenshiro traveling from place to place and fighting local gangs, or fighting the henchmen of the current antagonist, who are harassing the locals. Jojo, also from that era, even in its later iterations still does a "Stand battle of the week" formula until it is time to face off with the main antagonist. Heck, there is a popular series right now called "Demon Slayer" where the main character just fights X number of evil demon henchman until it becomes time to fight the big bad. Berserk easily could've gone the same way if Miura wasn't so creative. I don't mean to make too fine a point about this, I just think it speaks to how good of a writer Miura was.
Sure, I'm aware of how formulaic many manga are. That's why Berserk is the best!