I don't understand this "upside" variation vs "downside" variation. It seems like the same thing to me. My gas car gets stuck in traffic sometimes and will vary

I don't understand this "upside" variation vs "downside" variation. It seems like the same thing to me. My gas car gets stuck in traffic sometimes and will vary regardless of the roads. In fact, that variance described was on the exact same commute, due to differences in time of day, traffic, and weather. Often it gets over 30, sometimes well under it. It really isn't so different from electrics in practical terms.