Ok, this I understand. What I mean is that given that the Universal Prof covers all those things & the Arch Militant starts with them why are they then listed in the advancement profile, I can't see any reason to take them.
You can't take them. They are technically already taken by the character from the beginning. They did the same thing in the errata for Dark Heresy. In the first prints the talents and skills that PC's began with weren't listed on their first rank (well at least not most of the time), but somehow it was decided that the talents and skills that PC's start out with should be listed on the first rank along with the additional skills and talents you can buy. Probably for illustration purposes, to give both players and Gm's a good overview of exactly which talents and skills that any given career path will have access to, without having to flip back and fourth between the character creation chapter and the careerpaths chapter.
So for the Archmilitant: yes the Universal weapons proficiency talents are listed, but you can't buy them because the character has by default already bought them.