In the settings tab with Advanced setting checked, the Rebuild collection button will download everything you own from Totem's server.
NOPE, that is not the Function of the Rebuild Collection button.
Rebuild Collection Takes an Inventory of What you Have on your HD, and make your My Collection View, Match the Inventory.
It does NOT DOWNLOAD your collection.
Never has
It Might try to Download Missing Card images for the Data folder.
But it WILL NOT download the animation files.