Very good!
It is a pity the old forum is not accessible because we had lots of discussion around those.
The benefit of fullwidth punctuation is that they have the same box size as all characters, as required, and that they also rotate properly in vertical text.
They also belong to CJK punctuation pane for most of them, by the way.
Sometimes I think I have used a character called double exclamation mark also when I saw them like being in a same box, oblique.