Originally Posted by
blurrrsotong
So why did AB come up with a separate "THS" linear scale (and its added confusion) instead of just letting the MAC be?
Because although the two items - cg position and takeoff trim setting - are related they are NOT the same thing. If they always presented tail angle as "equivalent MAC" then you'd get all kinds of confusion, because that flap angles other than for takeoff the relationship doesn't hold, so someone landing might be confused that their "stab equivalent cg" wasn't their "real cg".
Stab angle (or THS angle, or units) is what it is, it's what the display shows you and what you need to set. I think pretty much every aircraft with a trimmable stab uses a direct indication of stab position, not some kind of cg equivalent units.