I wouldn't call the weld a completed weld until both sides of the joint are welded for starters. Secondly, 6.11 addresses the waiting period for A514 and A517, A709 grade 100 and 100W steels. These are low alloy quenched and tempered plate with minimum yields of 100 Ksi typical hardness of BHN 235/293. This is much different than A515, which is a low carbon, as rolled steel with a yield of 30/38 Ksi. The main reason for the 48 hour hold imposed on A514/517 is to allow time for hydrogen stress cracking to take place if it is going to (the high yield steels are very susceptible to hydrogen cracking). A515 is not especially sensitive to hydrogen. I'm afraid the engineers are right in this case.