Based just on seeing that sort of thing on other Hondas of the 1970s era: those steering stops were welded on by hand for a long time. And, holding it in position while you tack it on to start with your eyes closed (or the welding helmet closed: they didn't have the modern auto-darkening visors like we do today) it was common for them to be on crooked, out-of-position a little, or tilted. If it was beyond a certain point of error you could see where it was either broken or ground off and re-welded again, at least on the CB/CL72/77, CB/CL/SL350/360, CB450, CB500/550, and CB750 frames. I've seen that many times. Sometimes it would be 'corrected' by grinding it off for reweld, or sometimes, like yours, the front edge would just be ground back until the steering head turned like it was supposed to.
And then, not to leave them out, there are the garage-builders who just added an aftermarket gizmo to the bike and discovered it needed more "turn" on the handlebars to meet their desire? Seen lots of that, too, over the years.
