Yes, that’s right (sort of).
Hedgehogs don’t hibernate because it’s cold, per se. They hibernate because, as the ground cools down and hardens, their primary food source is depleted (caterpillars, beetles) In very mild years, it’s possible that a lot of hedgehogs won’t hibernate.
Trouble is, autumn juveniles will weigh around 2-300g now. That’s very unlikely to be enough time to put on enough weight to successfully hibernate if/when the cold snap does come later in the year - especially since all the local hogs will be stuffing their faces every night with the aim of fattening up. It means the small ones have to walk further and further to get food, expending more energy, thus not putting on weight and so on.
So, I’d almost reverse your advice. If you see a very small hedgehog/you’re in doubt it’s worth popping them somewhere safe, then checking with a local rescue. You can always release them the next day The problem occurs when people go grabbing hedgehogs that stand a perfectly good chance of piling on enough weight (I.e. around the 500g mark at this time of year).
it doesn’t help that not all rescues agree what a sensible weight at this time of year is, so there can be conflicting advice out there.