The extra threads don't affect the function of the fitting. As long as the O ring seats on the flange, and as long as the flange is not damaged, it will seal. Some of the GM fittings from FWD applications have a similar amount of extra thread.
Summit has hundreds of fittings although I'm not sure if any are shorter than the one you have now.
https://www.summitracing.com/search/...%3Amale-o-ring
Maybe these are better?
https://www.summitracing.com/parts/clp-605anf-or
Question: Would you be opposed to putting an O-ring fitting directly on your line and skipping the adapter? There are tools that can form the O-ring fitting on 10mm and 3/8" tubing. I've cut existing fittings off a length of tubing in order to form the tube into what I need.
https://www.toolsource.com/flaring-t...t-p-91005.html