The art of packaging

My brother broght me and pa a can of tea (Tie Guan Yin 铁观音) that someone gave him as gifts. He showed me the funny packaging. The top cover is supposed to be pulled over and it is typical if it is vacuated (typical for top-class tea with serious packaging). But then he showed me that the bottom can be pulled over easily. It therefore doesn't make sense to have a pull style as if it is vacuum inside. Our hypo is that the top cover has no functional use. The tea bags should be put in from the bottom and then they just put the bottom cover in place.