That's not clear. Eliezer contradicts that in both the articles and the comments. Others mention a private draft of an article in which Eliezer makes formal arguments in favor of this position. There's also a comment which points to a google doc that enumerates all the times recently in which Eliezer has reference "dying with dignity" in recent public talks and articles. There has been lively discussion on LessWrong after April 1st which has taken this article seriously.

It seems that it was purposefully released on April 1st as an opportunity to introduce a controversial idea and as an excuse to go a bit overboard in the exposition.

The post is literally tagged “April Fool's”.

Whatever else you want to say about the implications of making valid points and criticisms under the cover of humour, it's still an april fool's joke.

This is addressed in the content of the post itself, and many of the arguments made in the comments. EY doesn't disavow the content of the article. Quite the opposite, he explicitly recommends internalizing the argument made by the article.