Reasoning:

• a few people have mentioned it can be a pain to try and fill log piles (it requires 16 clicks to put logs in, or opening a GUI and shift clicking / mouse moving logs into the inventory)
• we want to preserve the ability to place log piles without consuming all possible logs (because in occasion they are still used as building materials)

Summary:

• shift click log onto block = place log pile (use one log)
• right click log pile holding log = place one log into pile without opening gui
• shift right click log pile holding log = place all the logs in your hand in the pile without opening gui
• [shift|] right click log pile without holding a log = open gui