@vitaljik Disabling the admin bar in the backend is highly discouraged since it provides the ability to log out among other things like determining which user you are logged in as.
That top bar has almost always been a part of WordPress dashboard, this plugin is exclusively for managing visibility of what has been called the “Toolbar” and “Admin Bar”. Since controlling that only applies to the frontend, I can certainly add more clarification in the description of the plugin. It’s already noted on the settings page and the corresponding screenshot on the plugin page.
Most people using this plugin already know the context of the feature but it’s also clarified in the settings page (and screenshot on the plugin page) that it only applies to the frontend.
Every plugin that disables the Admin Bar have that same assumption and does not address specific visibility in the admin dashboard. I don’t think you need to give this plugin a 1 star just because it doesn’t fit your needs, but you’re welcome to try other plugins out and see if you can find one that controls that within the admin area.