The older frames that have pins probably have them because they were brazed in a hearth, with a huge air-gas flame. They prevent the tubes from flopping around and sliding off, as far as I understand.
I'd love to give pins a try. But it seems you need an accurate jig to match the holes in the lug and tube, while the joint is in the proper alignment?
You drill the holes in the tubes and lugs simultaneously. Then pin that hole then move to the next hole, pin that, etc. I guess you could pin a frame one pin at a time while holding it in a vice, align, pin again, etc.