To be clear: an app can make it possible to do end-to-end encryption, so if it does, it's not a lie for them to say their app makes it possible

But an app can't make its own encryption end-to-end, so if they say their app "does" end-to-end encryption, or just "has" it, that's a lie

It being an app implies it's something can be transferred as a simple file between different users and run on their different systems, not something that can do encryption on its own in 2 places and thus ensure it's end-to-end