How is that difference meaningful? What actions are you going to take differently at 95% cloud coverage vs 100%? I can't think of anything I'd do differently if I was expecting 100% cloud coverage tomorrow to wake up and find that it was actually at 95%.

Yeah, and I’d argue that if the difference is meaningful to you, then you probably want something more accurate than what a consumer-grade weather service can provide. So it would be borderline irresponsible of Apple to even give you the false confidence of some precise measurement of cloud cover.