And the moment one runs into a player who is much stronger, they stop making the right moves that one could learn from for one reason or another and start making moves they know they can't get away with during play with a same level opponent.
Without seeing the games in question, it's hard to tell if this statement has any validity. As others have mentioned, games with high handicaps require the other player to play more aggressively than normal. And there is nothing in the rules (or etiquette) of the game that says a player must play corner, sides, and then center. Certain servers also lend themselves to an all out fighting style; again, different cultures play differently. But you CAN learn from the moves the person is playing. Perhaps you aren't learning about "proper" fuseki, but you can certainly learn about life and death. Every game you play is an opportunity to learn. A game that you lose is generally a better opportunity than one you win.
Meaning he only wanted to play with me to score a fast win and keep his precious Dan grade.
This seems to be assuming the worst about the potential player. You could be correct, but perhaps he (or she) wanted to offer a teaching game to a new player. Maybe they just wanted to play a game and didn't care who the opponent was. If you don't feel comfortable fielding requests from different players, most servers have an automatch feature that will find an opponent around your level. IGS certainly does, which is what I assume you were playing on if you ran into a 1k+.