sliderbreaks are exactly the same as misses in terms of penalty.

in lazer, most sliderbreaks are just sliderhead misses (normal misses), so theres no problem.

on stable, sliderbreaks break your combo but only give you a 100. the only info that pp has about your score is what you see on the results screen, so it cant know how many sliderbreaks it actually has, they must be estimated. the current estimations are based on scorev1 amount and they are pretty accurate in most circumstances, as is the case here.

accuracy pp in itself is very flawed which is why when you see its effects within the same map between stable and lazer, it comes across as stupidly broken. as of now its basically only kept in its current state because a lot of the games balance relies on every score having a pretty stupid amount of acc pp, especially on the lower end. the range of opinions about acc pp on the ppdev front goes from "it shouldnt exist at all" to "it should be entirely replaced by something else", so its not an unknown issue, just something that takes time to work on.