Oh, so that's what is meant by "semi-scale"
... oh well, thanks. 
Just my speculation - no hard facts. I think they call their couplers semi-scale because they, just like McHenrys, resemble the prototype AAR couplers more closely than other N scale knuckle couplers, like MTL, Acumates, Katos, or other clones (appearance-wise, not size-wise).