the rank 2 soldier types are added into the random bronze order pool. meaning that you can get them from bronze orders, but you are equally likely to get a rank 1 as it is random
when merging soldiers in the academy it is completely random which one of the three soldiers you get back at a higher level, so you might get either one (uneless you do 3 rank 2’s or 3 ranks1’s)
also, when you unlock the squads with for example engineer 2 or rifleman 2, you will only get one of those soldiers at said rank, and you will have to get more through orders
This may help you a bit.
BTW, even officials dosent know what to call those stars? ranks? tiers?
In game Logistics stars are tiers, but in news it called ranks, and sometimes it is called as “class”…