I think this discussion comes up when you compare it to the original SLDF: even those who wanted to enter the Quartermasters corps had to undergo basic military training.
I would assume that a good portion of the merchant caste never undergoes military training (unless they are failed members of the warrior caste). And I think techs and other members of IS militaries also undergo basic military training just in case a military operation goes south
That gets into the differences between the IS and Clan. In most situations the Clans just don't trust the lower castes with weapons and training.
For those lower caste who work within the Touman, they are probably expected to maintain a lot of military-esque aspects. Physical fitness and other things, they may have some version of a uniform even, and elements of military discipline. But they really just aren't combatants, that caste difference is very apparent.
It also means how they are treated on the battlefield by the warriors (of both sides) is very different.
I once portrayed a fanfic story where some Clan elementals overrun the rear area of their Clan opponent, think field base with power generators, repair equipment and the like, they encountered a lot of techs belonging to that other Clan. They didn't indiscriminately gun down the lower castemen they encountered all over the place. They ordered them to stand down and surrender. The lower castemen in turn, unarmed and with none of their own warriors in sight, obeyed. They stopped their work, allowed themselves to be corralled where the warriors told them to go and waited to see what happened, whether they would be claimed like Isorla by these warriors from a different Clan and become members of that new Clan, or whether their own warriors would show up and liberate them.
The only ones who died were under the direct command of a warrior telling them to get a particular piece of equipment working, and the elementals gunned down that warrior and the lower castemen adjacent to that warrior died as well, as antipersonnel SMG fire from an elemental sprayed the lone warrior and also hit the nearby techs he was commanding. The rest of the techs at the base were brought to a building and room, sat down and they waited under the minimal guard of one elemental. Later their own Clan's warriors showed up, retook the area, liberated the techs and put them back to work.
In all of this, the non-combatant status of the techs was pretty well-respected by the warriors on both sides. That had the benefit of keeping most of them alive throughout the whole ordeal. They don't jump in to fight, they don't intervene. If they are actively being massacred or executed it's entirely possible they may choose to defend themselves or run away (I mean that's just human instinct to a horrific situation). But that's not the Clan norm, it's not how they are trained to handle that situation according to Clan norms.
If it had been an Inner Sphere conflict between Great Houses, the support staff would have taken up arms, fought back, or retreated/would have been routed, and probably a lot of them would have been killed or taken as POWs. They would have instantly been transformed from support personnel to combatants once the fighting reached them. With Clan norms, that generally isn't the case.
I'm SURE there are exceptions to this. We know there are. The techs of Snow Raven Retrieval teams (R-Teams) are trained go onto the battlefield and begin their salvaging work before the battle is even over, and are trained to defend themselves (per FM: WC). I think the rules get pretty murky for a warship crew (largely made up of lower castemen) that is being boarded. They report directly to warship officers/warriors who might just order them to resist and fight. I can also see the rules being murky for combat engineers, who may be lower caste (but I can see this being an excellent place to put test-downs and solahma warriors as well), but still put on the battlefield to build that bridge, or whatever else, right amid a raging battle, where the opposing Clan might want to stop that effort.
So there are exceptions, some murky gray areas. But overall, it looks like this is how that is handled. That acknowledged Clan cultural norm also acts as a kind of shield, a layer of protection, and provides a layer of argument for why the majority of lower caste working in the Touman don't need weapons or weapons training. If the warriors recognize that you are unarmed and that the norm is that you'll behave this way, then the fear/urge/motivation to just mow you down at the first impulse comes down as well. Those lower caste begin to resemble civilians, or hostages if you prefer to Spheroid eyes. Easily controlled, obedient, even to the warrior caste of the opposing Clan.
