AHA! I think part of the problem is that you and I are talking "apples and oranges." I only use the term "pin" to mean the final application once uke is planted face down on the mat.
It is very possible, and not unusual in my experience, for a person to do an excellent ikkyo or nikkyo opening and takedown but still blow the final pin.
And one way to know the final pin is not effective is when uke kicks legs up and over the outside shoulder and rolls out of it.
That is a very good point. You really can't start calling it a pin until it... pins!