Absolutist Principles
Two bullet points, and the second is the one that matters. First: friendly BULLGRYN SQUAD, OGRYN SQUAD and RATLINGS units have ABHUMAN. On its own that does nothing, because it is a keyword grant that exists so the second bullet has something to name. Second: friendly COMMISSAR models can issue the Take Aim! Order, and can issue 1 Order to a friendly ABHUMAN unit. Read that precisely, because it is widely described too loosely. It is COMMISSAR models specifically, not Officers in general, so a Cadian Castellan or Lord Solar Leontus gains nothing here. The Take Aim! grant is a separate clause from the ABHUMAN grant, so a Commissar in this detachment can issue Take Aim! to any unit it could already order, not only to abhumans. And the abhuman Order is one Order, which is what turns a Commissar from a Battle-shock babysitter into a genuine order source. The rule text also states that this detachment has the ABHUMAN tag and cannot be taken with another ABHUMAN detachment, which blocks Grizzled Company, the faction's other abhuman detachment and the one a reader is most likely to reach for alongside it.