If its a duplicate bug that means others have reported it before in sufficient detail. Reporting it again adds unnecessary work if they are forced to address every complaint individually. When they deem it appropriate to discuss, it will be discussed. Many factors you are likely unaware of must be considered before said responses are allowed to go public, if ever, such as security, timing, or factors like intellectual property or public relations, and many other factors.

Their policy is not only perfectly ethical... it is also very common in the industry.