A lot of times, if you pit a player character against an enemy, both with equal stats and equipment, the player will almost always win due to being controlled by an actual human being instead of the computer and a set of code. One of the ways to more or less even the odds is to give the enemies special perks.
A notable example of a game using this method for balancing is The Elder Scrolls V: Skyrim. Unlike the previous installment in the series, the random bandits and marauders across Skyrim don’t have their equipment scale to the player’s level, which makes sense as it would be rather strange for small-time highwaymen to possess equipment much better than the Empire’s Legion.
At the other end, a decently high level player can easily be killed by a bandit chief wielding a rusty iron battleaxe for some strange reason. Partly for realism and practicality, giving enemies these ‘Extra Damage to Player” perks prevents one from running around slaughtering bandits across the land and selling their armor for easy profit. Of course back to the previous point, getting killed by an iron axe is rather shameful and frustrating for high level characters, especially ones that are practically wearing dead dragons. This is kind of relieved by having different types of bandits, with the really weak ones dying with so much as a breeze blowing on them to the tanky chiefs who can take a greatsword to the face multiple times.
It could be called an unfair advantage, but could you really say that if you’re the human here? Special perks for enemies isn’t the best solution- I certainly don’t have any alternatives to offer- but it works fine.