I agree. According to reports, Harry was upset that William referred to taking time to get to know this girl - that is, the language was objectionable to him. But the advice itself was perfectly reasonable.I think an argument can even be made that he was right. While this isn't specifically about getting to know Meghan, if they had taken it a little slower, they might have had a smoother exit à la Madeleine and her husband. It sounds like it would have been preferrable for everyone involved.
If the British royals hung out more with their European counterparts, maybe Harry could have called up Madeleine for some advice, and Meghan could have spoken to Queen Letizia about moving from a high-visibility career to being a royal (though Letizia was a journalist, not an actress). And everyone should call up Letizia for wardrobe advice. She and the girls dress so well!