It's pretty easy to get. As you say, there are HOF games, and Prince games in the Game of the Month training series and, frankly, any game by a Prince player who wants to see how well they can play before (or without) moving up in levels.
If someone is happy on Prince, and just wants to improve their Prince skills, they are perfectly entitled to to do, and to come to these forums seeking advice. Not every player needs to push the level at which they play, either for their own sake or to satisfy the expectations of strangers who cannot fathom why someone would be content to keep playing on Prince.
And let's tone down the arrogance a bit -- Prince is not "the least competitive setting". Last I checked there were three levels below Prince.
There's nothing wrong with that, but I do think a disclaimer needs to be made with certain pieces of advice. The fastest wins on high difficulty do not come from delaying settlers and building the GL. Fastest wins on low difficulty when you can't get science from trade routes and can't steal tech from the AI? Well then sure, obviously the fastest wins are going to come from getting free techs because that's the only place you can get them from.
But there's absolutely nothing wrong with questioning things that simply fly in the face of standard logic of high difficulties.