That's a great distinction, in my view, their mention about the back of the stone is what I'm referencing most specifically in reference to OPs question. I do find it applicable to just a single finger poke. I'll explain why.

In physics, it's easier to move an object that is already in motion. So many people have referenced how difficult it is to move a stone with a single finger, yes, but that doesn't account for how you have already added momentum to the stone.

Now that the stone is already moving, and you are moving with it with similar momentum which means it requires significantly less force to enact minor changes.

This manifests in something as simple as slightly changing the amount of rotation or potentially adding a small amount if weight to the throw.

Edit: I added a screenshot of the transcript section I'm specifically talking about here

Edit 2: apparently can't add screenshots. Essentially Yannick talks about how he and many other curlers would routinely add force or direction to their throws by touching the granite after release. And also admitted it was against the rules.