The QL data shows the case length, volume, and max pressures are different.
I don't know the true spec differences but if you make those two the same you should get similar output.
A-Square submitted a sample cartridges and drawings of a new factory chambering to SAAMI in 1996 to establish the round as the 6.5-08 but Remington go their hand in the mix about the same time telling SAAMI they were going to standardize the 6.5 version of the 308 with the same case (Remington 260) and Remington won. Exteranly the same but there may be some internal differences.