Those 3 pin razors that I have, often have very thick tangs a the shoulder. Those would rub against the scales at the logo part. I have re-scaled them with the third pin, I tried without and the rubbing was noticeable. Otherwise, there would be the problem of making the wedge angle so great as to make the width of the razor scales ungainly??

I think also, that it may have been to save bluing or gold wash from being rubbed off the tang.

Then, the three pin idea may have been continued to mark a quality razor even with out tang coloration.
Jut guessing from my experience.
~Richard