To me, the <partintro> element has the same semantic
value as <chapter> inside the <part> element, and it
should deserve a <partintroinfo> as <chapter> deserves
The problem arose when I had to write a revhistory for
partintro. Adding it to the partinfo element itself
would produce a revhistory for the whole part which is
not what I want.
Given the rich content available in a partintro, a
partintroinfo seems reasonable to consider.