You are correct. If the flow of traffic in lane 1 or 2 is faster than the flow of traffic in lane 2 or 3 then it is okay to pass. Intentionally changing lane temporarily to pass a car on the inside is illegal.
The other poster confused your point.
If someone in lane 3 is going 69 and overtaking someone then there's no reason to pass them, and probably isn't safe or legal given there is, by definition, a car on the inside lane already.
You sound about as self aware as the adults they're referring to.