I think one potential scenario to consider is that the core roles for the NGAD and F/A-XX may now be flipped, where the NGAD is the lower-tier lower-cost design, while the F/A-XX is meant to be the true top-tier challenger to the CHAD and SHAD.
I think what is becoming increasingly clear is that in 2019-20, when the first US demonstrators were flown, there wasn’t really a clear and coherent view within the US industry or defence establishment on what next gen fighters primary overriding design priorities should be. So what was flown was more of an evolutionary step forwards as opposed to a true revolutionary leap like the CHAD especially, and to a lesser extent, the SHAD.
The NGAD is basically 5.5 gen, where the thought process appears to have been that with both sides having 5th gens, detection ranges will shrink, so more likelihood of WVR combat, hence the canards.
It’s kinda amusing that the roles of the US and China seemed to have now flipped, where now China is the thought leader and America gets the benefit of being able to copy China’s homework.
The priority for the NGAD is to get in the air ASAP to not allow a generational gap to emerge between the PLAAF and USAF, even if only in name. I think the F/A-XX might be the clean-sheet design to truly take into account the new air combat vision the CHAD envisions.
From an operational standpoint, it also makes sense for the US’ true answer to the CHAD and SHAD to be carrier based, since that will be the most likely engagement route for both sides’ 6th gens to engage in combat. Although the carrier requirement will undoubtedly place significant design restrictions and limitations on the F/A-XX, so it can’t be as large as the CHAD.