Well honestly in the recent time I've seen more of April Fools events in the manga and anime scenes, although turned out there are surprising amount of April Fools VNs. Other than those three, there are the other two that are particularly stick out to me, Shakadou-san no Jun'ai Road and Seventh Coat. For more elaboration, Seventh Coat is the April Fool VN for Fata Morgana with the developer change the genre from fantasy to science fiction, while for Shakadou VN it's the parody of Tsujidou with Shakadou (One of the antagonist in Majikoi) as the MC. Note that the developers for both put some efforts into those VNs, with Fata Morgana writer tried to make Seventh Coat writing as good as possible while Minato-soft hired Hanakana of all VA to voiced the main heroine of Shakadou (Kugenuma Sakura).
I think that's all for what I can comment in regard of April Fools VNs.