4.2.2. says that if the user can enter content using the keyboard they must also be able to exit it using the keyboard, even if the content uses a non-baseline technology. This helps, but is not a complete solution, because it does not require that the keyboard method be discoverable by the user, especially if the user has a disability (e.g. a screen that cannot be read by a screen reader displays "text" telling the user they can exit by pressing F10, but the user who relies on the screen reader has know way of figuring that out). This is addressed in Techniques, but I fear that is inadequate because such documentation is so critical.
Change "If content can be entered using the keyboard, then the content can be exited using the keyboard." to read: "If content can be entered using the keyboard, then the content can be exited using the keyboard, and the method for doing so is described using technology in the baseline."
Thank you for the suggestion. We have modified the success criterion to address the issue that you raised: If focus can be moved to technologies that are not accessibility supported using a keyboard interface, then focus can be moved away from that content using only a keyboard interface, and the method for doing so is described before the content is encountered and in a way that meets all Level A success criteria."