You have put it well.
Do you mind if I insert (AND UNITIZING) and see if it meets with your approval. I am using uppercase to show it is not your words but mine. I am “not” rewriting your sentence, I am just asking if you agree with my insertion?
“But Tschichold had to adapt to both constraints — duplexing (AND UNITIZING) for Lino, unitizing for Mono. So he made the choice to make the two ‘a’s ﬁt the 9 units (which yields a noticeably wide roman ‘a’) instead of cramping the italic in the 8-unit slot.”
Unless systems in Europe were not equal to America? I refer you to Mike Parker