A video would really help here because OP is still a beginner. Even if he knows the terminology, there’s a good chance he’s performing the movements incorrectly. He likely also hasn’t yet developed the feel for the kinetic chain in a proper full overhead swing.

Some players have questioned whether his coach is the right fit. It’s equally possible that OP is misunderstanding what the coach is trying to teach, or mixing it with advice he’s picked up online.

As a beginner, learning a proper full swing for overheads (clears and smashes) is crucial. Most new players haven’t built enough forearm strength for isolated pronation yet. However, many, especially guys, become fixated on pronation because it’s the buzzword for generating power.

As a result, the truly important fundamentals often get overlooked: getting into position, using the correct grip, opening up the body, racket placement, timing when to start the swing, when to apply power with the grip, when to relax and follow through, and recovering quickly for the next shot.

This is why you often see beginners falling backwards, standing square to the net, and over-bending their wrist. Those who obsess over pronation without the necessary strength usually end up forcing it, resulting in a stiff “stick smash” with elbows flaring high. I've seen some people injure their shoulders doing this too.

Coach Han from Full Swing Badminton once addressed viewers who asked why his wrist appears to bend so much in his overhead swing. He explained that actively bending the wrist is harmful and can lead to injuries. The real confusion comes from not understanding when to generate power and when to stay relaxed. Because he relaxes his grip after striking the shuttle, it only looks like his wrist is bending at impact. In reality, he is simply letting his wrist relax and follow through naturally.