2-p, I agree with the yield and ultimate tensile you quoted. The catch is that the stress/strain (load/stretch) is similar for high and low tensile steel. However, the low tensile will yield at a given load whereas the high tensile steel will continue to stretch under increasing load without yielding. The hard steel has a higher yield point only by virtue of a greater stretch. So, as I see it, it is adding no extra strength beyond what it would add if it was soft.

DDA