Android app limited offline

[saxicola]

I have plenty of time while commuting so I like to do DL on my Samsung tablet, but without an Internet connection. However I find that without an Internet connection the only lessons that I can access are those in the line of tree skills I have reached. Everything else is greyed out. This is annoying as it means I can't do any practice and once the available skills are complete I can't do anymore. Is this normal or a bug?