When being observed, a door which is opened by the player only triggers an update from the bottom block but if opened by redstone it updates both.

A door which is opened by the player only updates the bottom block, of the door, but a door powered by redstone updates both door blocks.

Video showing the bug

My theory is that it always only updates the bottom block when opened, but when powered by redstone it is updating the Powered tag so it triggers the top block.