For any half fit cyclist, the 25kmh ebike limit is the minimum speed. That is the speed you go uphill. Downhill and flats, you can go a lot faster, because you didn't spend your energy accelerating to 25.
But then you're on your own with a bike that weights at least 10 kg more than it should. I was in a group of friends. One of us had an ebike. He was good on our way to the hills and of course uphill. We had to stop and wait him a lot of times on the way back, because we were doing at least 30 and he was struggling to keep the pace without the help from the engine. I suggest not to mix bikes and ebikes unless you are out for a slow Sunday afternoon trip.
In a large enough group the body weight differences easily outweigh (heh) the bike weight differences. And of course the fitness differences are a whole other story.