Primarily for the recovery of the CT/OH is my reason. See, throws are fast in relation to attacks. Due to their speed, their triangle property is applied to the entire animation. Throws also have the smallest of active frames (2) and are generally around the 28 frame recovery range. That is, if you were to attack during their recovery you get a hi-counter throw, and you get counter-throw if you throw during their recovery. Holds are very much the same way where they have their hi-counter property applied to the whole animation. Throwing gives them Hi-counter during their recovery. Holds also are the fastest part of the triangle for 0 frames and their active window is the largest of the triangle, with the smallest of the recovery.
However, if you perform an offensive hold, the offensive hold is vulnerable to a hi-counter throw throughout its duration. Offensive holds at their fastest are at the speed of a mid-tier speed attack. So they're very susceptible to the even faster
Punishing an attack in recovery with an attack or a throw also nets Normal damage, regardless. Attacks have at most a faster startup than OHs, are generally with longer active window (3-5), and about the same recovery.
Additionally, ask anyone who sees an Offensive Hold for the first time and they will tell you it looks like a Throw over looking like a Parry.
The huge recovery window, low active window, and medium startup make me feel the "attack" shouldn't be hi-counter throw punishable at all of it's animation. It feels more intuitive that it be treated like a throw. It's counter throw if you hit at any point of the OH, Hi-counter if it lands against a hold, and normal against an attack.
I mean I can see both sides of the see-saw honestly, and the main reason I'm okay with it is giving a damage boost to landing a slow "throw" against a faster attack. However, OHs were how they were in DOA1 when the game started so I can't argue that it doesn't belong to be the way of CTs. CTs are what they were converted to for DOA2 and DOA3, and they were "restored" to OHs back in DOA4. It should be noted though that everyone in DOA1 had a 10-13 frame offensive hold though that gave advantage. Somethign I'd personaly love to see returned to Bass as it would give him SOMETHING to deal with the heavy attack game.