Absolutely...very important. Driving too fast on ice is very dangerous.
Although, I would argue it is even more risk to drive significantly higher or lower than the average speed being maintained by the traffic flow. If you do not feel safe at that speed...don't drive.
Stay home a few hours or days...let the plows get out there.
The main point of my statement wasn't about "what is a safe speed"...it was about the very clear difference of "speed of traffic flow" as soon as you get off of the pass. In the original case I was discussing...I had drove 300+ miles at 50-60mph (speed of traffic flow)...then the last 10 miles the average traffic speed cut in half (which was also the best weather conditions).
I made a comment about it to my friend when I got to Seattle and his comment was "yeah...people over here lose their minds when any snow falls"...up until that point I had no idea that was a thing.