So the rate of change of demand is decreasing. Decreasing rate of change is the definition slowing down. Although I agree that most people probably misinterpret the phrase as you say. (It seems other replies have had that interpretation.)
Increasing position less fast is the definition of slowing down, as I said. Increasing speed less fast is, of course, not the definition of slowing down, it's decelerating; we agree on this.
But you are equating demand to "speed" (rate-of-change of position), and I am equating demand to "position" (not a rate-of-change). If demand is analogous to speed, then what is is measuring the rate-of-change of?
Acceleration decreased such that it is negative. Negative acceleration is "slowing down."
Ok, let’s substitute that into the original comment, instead of:
> demand has slowed down recently
we get:
> speed has slowed down recently
Nothing to do with the rate of change of speed, just speed itself. In other words:
In terms of _speed_, this would indicate that _speed_ was once higher and is now lower.
Let’s translate that same sentence back substituting speed with demand:
In terms of _demand_, this would indicate that _demand_ was once higher and is now lower.
That statement cannot be true as 2023 demand was the highest ever.
Where it could be different is in places like power generation. You might talk about peak demand in Watts, and daily demand in watt-hours.