That is correct. We added the tear-drop sections of tube after doing fatigue testing. I think there were a couple of early failures revealed by some of the heavier guys who liked to get some air while riding.
The added benefit of torch brazing the tear drops was that the heat from brazing helped to stress-relieve the welds that joined the short tubes of the crown to the fork leg tubes which were subjected to the highest level of stress on the fork.
We never did any metallurgical study to confirm this, but failures were drastically reduced. This also gave Chris the confidence to produce the Big One Inch fork which is now prized by collectors.
Wish I was smart enough to have built one for myself - oh well
I'm really not sure how many Yo forks were made that don't have the tear drops. We didn't keep good numbers on forks and none of them were serialized as far as I know. I pushed for it, but it never happened (at least in Somerville).
Good luck and keep a close eye on the back side of your fork where the short crown tube is welded to the fork tube. The most likely spot for a crack to develop will be right next to the weld in the fork tube.
Regards
Scott