I asked @NihonGo: "Do you also write these extreme Kanjis with 56 or 88 strokes in these 1cm squares in Genko Yoshi paper? How is that supposed to work?
Examples: search 'most difficult kanji' "
------> Answer: Theoretically yes. However, they are rarely used. It is more common to use the "Jōyō Kanji List" in everyday life.