1: it's not a "tutorial" it's a review. Not everyone will understand the mechanic and instead they just fumbled through the level, so it's there so that everyone is on the same page after a level. If the review were at the start of a level, it would spoil the discovery part of the puzzle. That's the best part! It's like spoiling the climax of a movie!
2: You seem to fundamentally misunderstand how the mirror gem works. Were you actually reading the "tutorials" you were complaining about? That's besides the point. The fact that the mirror block doesn't work "intuitively" is the exact point. This is a puzzle game, not a shooter. You're supposed to be solving the puzzles using information, not intuition. And besides, if it worked exactly how you expected, you wouldn't have that thrill of discovery that puzzle games are designed for.
TL;DR: bad opinion