French vs Italian Down Tube shifters threads

[Foreigner]

Why would the nut on Campagnolo DT shifters not thread into braze-on, but Huret one goes in pretty easily. At the moment the combination of both as per pic below is on the bike, but it does look little out of place to say the least. Also not sure on how it will function if at all?
Retaping threads needed? Really don't want to use heavy steel Huret shifters that they were originally on. Suggestions?

Many thanks

 

[many408]

Let's have a pic of the naked braze-on; it might have no flats on the post, which the Campag shifter needs.

 

[Woz]

Re-tapping the internal thread is generally not recommended (I've read).

https://restoringvintagebicycles.com/2017/08/21/french-threaded-shifter-bosses/

Removing the plastic wings, replacing with a washer, and shortening the nut would work.