At the WWDC2016’s Part 1 session of what’s New in Metal, an iPad was used by Apple for the demonstration of the graphics API’s capabilities for the new adaptive tessellation on iOS10. In the video, on the 17:58 mark, the icon of the TextEdit could be seen on the home screen of the iPad from the app switcher screen used for multitasking.
Though the mobile version is yet to be released for the iPod touch, iPad and iPhone, however in some of the OS X previous version and the macOS Sierra, the TextEdit is pre installed by Apple as it is a basic word processor. In the screenshot, it was also seen that in order to fully match the app, there were no third party apps available.
The Preview icons and TextEdit were spotted previously in a screenshot of the pre‐release of iOS8, however neither of them were part of the software update for the public version. A report that had been released early in 2014 stated that both the apps were said to make a debut as a read only document for viewers who were using iOS. From a Mac, the files of the TextEdit and Preview were stored in iCloud.
There is a chance that now Apple has plans that on the iOS; they will release the basic text editor to complement Pages and Notes. The explanation that can most likely be given is the fact that the TextEdit is like a testing app which serves like a simple Hello World for internal developers. The employees and software engineers have various internal apps that are used only by them which are provided by the company. Even the Game enter could be seen even though on the iOS it is said to be a standalone app. The first beta that was seeded for the developers was previewed during the WWDC keynote.