Yup. Heating and cooling are 2 things that can be delayed in most cases with little negative effects. A hot water tank set at 60C isn't going to be harmed if it's allowed to cool to 55C due to high power demand it also doesn't instantly empty out with usage.

The same is true about climate control. 1 or 2C from the desired temperature is still pretty comfortable but can make a huge difference in power savings, particularly if it's coordinated.

That said, I suspect that the even better route for power companies to go down is installing more grid batteries. Those can directly address and smooth out high demand. Put them at the various substations and you can shut off the main grid to the substation temporarily under high load.