I think it is somewhat odd that all our Non Hackable Heavy Infantry can be stopped with E/M Ammo. Or am i missing some important rule here?
no, they are HI and are not EM immune. Note despite what you may perceive, even ariadna HI are near future, a EMP would do a lot to much modern military forces, the type we'll see in the next 50 years or so even more so.
And is that effective with current technology? Not really, so that tells you those armour plates are more than youd expect. Typically they are a tessium alloy and tougher than steel.
I did not question that the Armor is of more advanced materials than today. I only question that you can be stopped by E/M effects while you are wearing todays infantry armor with mor advanced materials. But you answered my basic question. Fluffwise it is up to debate.
There's some fluff in various places about how even Ariadnan heavy armor is servopowered (please don't ask me for page numbers), so it's vulnerable to EMP. But it's not hackable due to not using quantum processors like even civilian tech does in the Human Sphere (though I should point out that military electronics tend to run 10 years behind civilian, minimum).
History tells that Military tech is of two kinds: nearly obsolete, or so brand new it has been stashed until the obsolete one breaks down and the new one is used... usually when it is now obsolete by at least one generation of development. Mind you, I just go in my mind with "Teseum + E/M means it becomes heavily magnetized", so the HI and TAG gets "frozen" XD
That could be a reason for Vet Kazaks being able to use Mk12 despite the fact that they are not augmented humans.