Chromium vs Android

There are a couple reasons why we open activities launched from Chrome with NEW_TASK flag. The biggest reason is that it provides a much clearer user experience: the user sees the new app as a separate entry in recents — also, if we were to place a different application on top of Chrome activity, the Chrome icon may end up opening that application sitting on top of Chrome, which is fairly confusing for the user.

Bug 445956, wherein the Chromium developers consider the Android task metaphor too confusing for users and work around it.