If it's not accounting for this difference, visible via the ETA, then please tell me. But as I understand it, you just don't see a red jam on it. To Waze, that 30Km/h at Rush Hour is normal traffic.
Like I said, the only quick and viable way to show these red jams would be to make the coloring of jams be dependent on <current speed>/<global average speed>. Right now, it uses <current speed>/<time of day average speed>.
The Way Waze works now, it's like the same as not having it. If I do not get information about speed or size of a jam in rush hour, is actually the same as not having waze. If you think about it, waze is only giving you an eta. I'm not seeing which way is faster so we have to trust waze that it is doing us the best route. But since it does some stupid routes, I can't fully trust it. And i know my town better than it. That's was the idea of the topic: if waze show us the road colors all the time it would give us a better feel about the route. If the speed average in rush time is 30kmh why not plot red in map ?