That's exactly the point. They did not have only 4 weeks for TLFR because they had something to deliver! As they are recording every show they do have an amount of recordings they could have thrown out if it all was just about the record company who wanted them to deliver something.

No, they got the idea of TLFR and WANTED to do it this way. That's why they were in a hurry - the idea came a little late. That's all I think.