It's a free service that they provide - why can they not change how their system works when they want? People can object whenever they want - but it doesn't change the fact that they don't have any 'rights' to show someone elses content via a 3rd party on their website.
Maybe if you paid to embed tweets? Sure ok, they changed the contract - so deal with that.
Is it a bit annoying if you use it? Probably. Is it bad that the docs are out of date? Ok.
Twitter doesn't have any responsibility to you as someone who wants to quote someone else via their platform.