The user should be able to sort a playlist by last added (songs) on mobile.
This is posible on desktop.
It is more likely that the user want to start to listen at the top of the playlist with the "freshest"/newly added songs, than on top of a playlist sorted by the oldest songs.
We'll pass on your comments to the right team.
Hopefully they'll make it more user-friendly. Let us know if you need anything else, we're here for you.
Take care 🙂