Pretty sure that the yield strength of brass is NOT set in concrete. There are many, many alloys of brass and tempers that all affect the yield strength. Now, if we are talking about one specific lot and batch of brass that has been treated the same it's whole life then absolutely it's a solid baseline as to what load/pressure is acceptable. 7 loadings would be VERY acceptable to me for high end loads.
By the way, I don't have quickload either but the data I've used from it seems to be accurate. I'm consistently a couple grains of powder over predicted velocities, which I will attribute to moly coated bullets.