That page is protected already by the "manage_options" capability; "advanced hiding" does not have any real impact on key security.

If a user has the "manage_options" capability and a technical background, he could also retrieve data in other creative ways.

If the security of the key is important, we may consider implementing some advanced strategies, but not this one, as its hiding is not actual security, rather just a little bit more security through obscurity. However, these implementations would not use any input fields and would require some more technical methods to define keys.

We're open to addressing any security concerns, but not with duct tape.