Hopping (at least in Apex) is NOT skillbased, it IS an exploit due to the variation in hitboxes. Fighting somebody like Caustic who has a massive hitbox, if he's jumping around it doesn't matter, his hitbox is huge and you can hit him regardless but a smaller hitbox such as Wraith? That's where it becomes an exploit.
We used to do the same back in Halo 3 on the Xbox360 for Team Swat (For those who don't know, Team Swat = one headshot kills with any weapon) the elite model had a head that swayed and bobbed as you jumped, it also left gaps in the hitboxes which made headshots on elites while jumping really hard to hit. It got to the point where most people would quit out of a game if they saw somebody playing an elite in Swat due to the blatant exploiting of hitboxes via jumping.
Hell there was even something called "Strongsiding" where you'd run and look at the ground so your head was ducked and the enemy couldn't hit it from behind. That's more of a skill based thing than hopping around as it only work if getting shot from behind and the downside was you couldn't see where you were going.