Fix setMotionType with Physics instances (#16880)

Author: CedricGuillemet

packages/dev/core/src/Physics/v2/characterController.ts

@@ -232,7 +232,7 @@ export class PhysicsCharacterController {
      */
     public dynamicFriction = 1;
     /**
-     * cosine value of slop angle that can be climbed
+     * cosine value of slope angle that can be climbed
      * computed as `Math.cos(Math.PI * (angleInDegree / 180.0));`
      * default 0.5 (value for a 60deg angle)
      */

packages/dev/core/src/Physics/v2/physicsBody.ts

@@ -252,10 +252,10 @@ export class PhysicsBody {
     /**
      * Sets the motion type of the physics body. Can be STATIC, DYNAMIC, or ANIMATED.
      * @param motionType - The motion type to set.
-     * @param instanceIndex - If this body is instanced, the index of the instance to set the motion type for.
+     * @param instanceIndex - If this body is instanced, the index of the instance to set the motion type for. If body is instanced but instanceIndex is undefined, the motion type will be set for all instances.
      */
     public setMotionType(motionType: PhysicsMotionType, instanceIndex?: number) {
-        this.disableSync = motionType == PhysicsMotionType.STATIC;
+        this.disableSync = instanceIndex === undefined && motionType == PhysicsMotionType.STATIC;
         this._physicsPlugin.setMotionType(this, motionType, instanceIndex);
     }