Afaik just old kana orthography. The sentences you mention are more than 100 years old, one of them is 300 years old. Writing reform was 1945. It is generally not useful to include these old and archaic forms. If they are included, they are assigned a respective tag, and they need to actually be mentioned as a spelling inside a major reference.
うずうず 163.310 99.6%
うづうづ 639 0.4%
Technically any ず or じ containing word can be written with づ or ぢ, same sound. But why do so?
There are only a select few modern common words still using them, e.g. ちぢむ, つづく
Just to be clear, when I say "づ or ぢ, same sound" I mean in modern japanese.
Thanks for telling me. I realize that the example I brought up was old, but I started the discussion because I encountered うづうづ (and うずうず by extension) for the first time when I was reading something that was written in October of this year.
I see, no worries. Might I ask where you encountered it?
other form: うづうづ
on the kotobank article for うずうず, one of the example sentences uses うづうづ