The purpose of any registration trial is to get the best possible marketing label.
As for ABBV/ANTA HCV products, they are considered/perceived to be inferior to GILD's HCV products. Consequently, ABBV has realized that no marketing (including price discounts) would substantially change the situation. This is why the ABBV head-on trial will make or break HCV GT3 marketing.
It is interesting that ABBV decided stay away from other HCV GT group. A success (the head-on superiority results) will lock GT3 for ABBV and also will spill a positive perception into other GT groups. A failure will not be a big deal for GT1 marketing.