Some of the fastest Event-goers have probably noticed that they are unable to access the EOs (E-4 and E-5) According to the official twitter account, the EOs will be implemented tomorrow (no date specified) [1]
Evidence to support this is also in the partiality of some datamined in-game files, such as the lack of Saratoga's damaged CG and Asakaze's too. Their stats appear to be missing, too. From the datamined files we have determined that E-5 Hard Mode will probably have a separate shiplock from the rest of the maps, however, if you opt for E-5 Easy or Medium then it should share its shiplocking tag with E-2 and E-3.
Again, this might be subject to change. We suggest you exercise caution and wait till tomorrow or the day after it so that we can get more concrete information on the event's true nature. That also applies to anything you read on the event pages, do not take everything written there as fact, be skeptical and do your own research around the wikia or other sites in order to confirm it for yourself. Looking for videos on various streaming sites is a surefire way, for example. We will do our best ensure that which has been written here will be true.
Good luck and fair seas, ladies and gentlemen!