Although I'd love to agree superslicer has sadly nowhere near the development power of prusa behind them - and feature parity is rarely given, basically any release of the two has "oh I want both of those!" (don't know if it's spelled correctly but arachnid mode for example was hyped to a point I checked back with prusa after a few months).
I just want to point it out in case people expect a "prusaslicer" but better in every regard :)
I can't answer that and it's a valid question in my opinion.
If I had to guess I'd speculate about disagreements in code style, build pipeline or similar.
Thats usually how it goes. Imo, and to be clear im a major foss person, they are contributing so they should accept the prusaslicer guidelines but maybe have an open discussion about.
I havent seen the prusaslicer code yet so i have no how bad either project is though :p
Oh yeah, I find that it's easier to get fine control of the outcome in SuperSlicer because it's less refined. User-friendly features are nice when you're getting started but a hindrance when you have more experience. I tried to use Cura awhile back and it felt like the Fisher-Price version of a slicer. SuperSlicer is probably less accessible overall, but it doesn't hide controls from me.