I feel like you’re still thinking of a closed system without the possibility to import or export. Maybe it’s a regional thing, I don’t know how many interconnects to abroad the US has. In Sweden this year, like in much of Europe, production is as close to maxed out as is safe, and peaks are filled by importing/exporting.
My original point was that, in regard to the ancestor comment “We'll still use that 0.5% for something else, right? It's not as if power generation (and emissions) will be reduced.”, yes it’ll be used, and no it most likely won’t be reduced. It will be exported to Germany (or some other country with a drastic electricity shortage) and used there instead.
That's not how it works really. The peak can change - it may literally be influenced by the break time in TV shows and people putting the kettle on at the same time. In the other direction, we may lose capacity due to repairs and unplanned outages. If we ever get close to 100% of production capacity for more than a moment, that's a massive planning issue. Instead we do rolling blackouts.