sure, just make a new world, go to the end, place an end gateway, restart the world and kill the dragon: no egg.
yes. It is used in determining if the egg is gonna spawn. You re gonna lose that if this happens. It can if somebody decides that they needed to place an end gateway before the Dragon was killed so people could get themselves elytras. That happened on my server.
i m using the termonology from the bugfix idc if it s correct i m unsure what to call what all the time i remember the properies it has instead xD
well ok, my wording may not have been accurate. i filed this not because it s a big deal, but because it isnt expected behaviour. for the portals it makes sense, but not for the gateways.