I would rather have seen it re-branded and having another pie added to the game.
So instead it would be like this:
Have teaching pie but re-brand it as “Knowledge pie” or something. Keep it as it is, except change so that the buff runs out while you are offline. This allows mining to continue as normal - but prevents logging out with it.
Create a new pie, called “Learning Pie” or whatever. This pie would work like the changes have now become. This pie gives double exp up to 70k exp or whatever.
This way, we satisfy all parties except those that want to log out with old teaching pies. We get more pies (diversity) in the game and the game gets another material sink.