The x-frame X-content policies are not handles the same way !
Hopefully, my server is a fully home made rig using debian and apache2. So i know what i am doing, witch is clearly not the case for one of the automatic tester
How did you end up with a score of 40/100?! NC15 brings 110/100 by default config (with web server config from the documentation).
Looks like you are using a badly configured proxy or something which terminates the headers from Nextcloud.
My post which you linked there is talking about another topic and setting up additional headers, but these additional headers just increase the score to 120/100.