Okay, rather than use examples, I'm going to go theoretical.
There's something I'll call "GM Force" that's basically the GM's ability to influence events in the game. In traditional games, this power is very broad; often it's defined as "anything outside the PC's skin".
I'm using Force as a neutral term here -- as in "force of gravity", not "forced to do something".
If you present a plot hook, have the party attacked by NPCs, or even tell them what the road they're traveling on looks like, you're applying some amount of Force. The only way you could GM without applying Force would be to never narrate anything, and only adjudicate player actions by looking in the rulebook.
I then define Railroading as "Force applied in a way the players are uncomfortable with". It's something that violates the social contract. The most common thing players are uncomfortable with is having decisions made for them, so telling them there are two paths but they can only choose one is Railroading.
Telling a player what their character does is Railroading unless there's an in game justification that the player accepts. So I think Charm Person isn't railroading if the player is okay with being charmed, and it is railroading if they're not okay with it.
Scene framing can be railroading or not, again depending on player acceptance. I've run scenes that started with the PCs having been captured "off camera", with the players unable to stop it. I don't think it was railroading any more than having them be attacked by orcs, because both were setting up a scene for the players to make decisions within. But if the players hadn't been on board with what I was doing, then it would have been railroading.
That's why I don't think in-game examples tell the whole story. Railroading isn't about what you do to Fizzgig the Dwarf; it's about what you do to Fred the player, and how he feels about it.
On a separate note: What about Illusionism? Some GMs will restrict player choice as much as a "railroad" would, without letting the players see behind the curtain. If you present the player with two choices, and play out the outcome the same no matter which they choose, is that the same thing as not letting them choose in the first place? Same amount of Force applied, but it's done invisibly, and the player believes that they have not been restricted.