Yes, it’s an Xpath bug with Appium. I have definitely come across this before.
The bug occurs because Appium is currently unable to associate a given WebElement with a given View in Android. There is also no API or framework available within Android for resolving Xpath queries against the Android view hierarchy. Thus, context-specific Xpath queries can not be resolved. Currently, it looks like they context-specific queries simply resolve from the root of the view hierarchy (unintuitive, yes?).
I think there might be a GitHub issue open for this somewhere on the Appium server project. I’m too lazy to check myself. 