This is the expected behavior in beta.6. See the "Explorer updates" section of the
release notes. You can now start the expression explorer by clicking anywhere within the expression. That is what is happening for you.
If either speech or Braille generation is enabled, the explorer can be started, so to disable this, you would need to disable both of those.
You can do that by setting the options.menuOptions.settings.speech and options.menuOptions.settings.braille to false. Note, however, that that will disable most of the assistive tools, and so you're readers who use screen readers, for example, will not be able to have it read your page properly. So you should only do this if you don't care about the visually impaired community.
Davide