Sim now seems incapable of rendering overcast consistently or accurately using live weather

Visibility to the horizon would also be a useful judge of how well it is represented. If you have it, it’s worth playing around with Rex Weather Force, though I think its overcast wasn’t as good as MSFS native. Other cloud types it was better for though.

Which from the ground can still be observed as 8 oktas, and therefore overcast.

I think that is what an automated weather station would report, rather than FEW016 BKN031 SCT042, an so on.