[otnt]

I would venture that 99% of Android tablet users do not have a mouse attached. The majority of Chromebooks don't have a detachable screen, but do have a touchpad and wouldn't use a mouse.  I don't think there is any point in prompting users every time the app is opened, as it applies to so few (and this would just annoy a lot of people). This seems like such a minor thing as well, as most users won't need to disable the mouse cursor. I think having a warning on the setting is probably good enough as most people don't venture into the "Other Settings" section anyways.

Thanks,
Mike

Exactly my words. Warning at the settings is more than enough.

I also tested Nexus 7 with 6.0.1 Android and the mouse setting is not showing up (great).
I also tested a phone with LineageOS 8.1.0 Android where the setting is visible but even when "Disable Mouse Cursor" is enabled and ticked the app would not show that blue bar or the mouse cursor (great).
So it probably is only Chrome OS behaviour.

Have you ever thought about creating special ChromeOS forum section?