Commonly school is teaching a method. "Getting the right answer" is just a byproduct of applying the method. If you tell your kid that they should just learn the methods you teach and be dismissive or angry about school trying to teach them other techniques, that's probably going to cause some issues downstream.

Techniques of an "intuitive" character often lack or have formal underpinnings that are hard to understand, which means they do not to the same extent implicitly teach analytical methods that might later be a requirement for formal deduction.

I hope that I wouldn't be dismissive or angry. My worry is that my son will feel dejected because he (correctly) thinks he understands something but is told he's wrong. I also worry about him getting external validation from following a method, and will value that over genuine understanding and flexible thinking. But I see your point that it's my responsibility to help him work through that and engage with the syllabus.