The van got to witness potentially 4 seconds of yellow lights/part of the stop sign opening before the van was no longer obscuring my view, 4 seconds of time I didnt have in relation to the view of the bus being blocked by the van. Up the hill further back the bus was on lower ground and was visible from a further distance, but as the ground leveled the van blocked what would be where the bus stopped. The bus didnt have hazards/stop sign deployed when I was witnessing them driving ahead before the van obscured the view.

Also why i emphasize the 150-300ft the driver needed, as that would have been plenty of time and distance to inform me and the van to slow down to a stop (compared to the van slamming their breaks and me being out of view)