This would have some impact on hardware sales, particularly graphics-related chips
That’s why a console manufacturer pays Rockstar for an exclusive.
Aren't they still on the x86/64 ISA?
Also while they are technically similar, it's still separate optimizing/QA work, so staggering release makes sense vs waiting until the work is done for all platforms. And maybe it makes the rollout for the online part easier if the easier-to-analyze/-hack PC versions come later.
GTA 4 was closer to eight months.