a-Shell is a terminal emulator. It runs entirely locally, on your iOS device. It does not need a network connection.
a-Shell does not collect any data, period.
You can use a-Shell to create and edit files. You can process these files using grep, find, lua, python, TeX... All of this will happen on your device and you will be the only one to know.
You can move the files created inside a-Shell outside of its own directory, into other applications directories. This is done by you, the user, as needed.
During the TestFlight phase, if the application crashes, a crash report can be sent to the developers. This crash report will contain information about what caused the crash (functions being called, values of variables).
The owner of the application, Nicolas Holzschuch, does not have any way to access the data created by the user.