I have no real idea of just WHAT they are planning for the BUFF but I doubt long range high altitude stand off for strike aircraft is part of the mix. I thought they wanted it for striking secondary and low defencive ability ground targets with iron bombs. As they have done for some time now.
My understanding is that the B-52 hasn’t routinely flown at low altitude for decades (at least in actual combat; a low altitude capacity probably being maintained via training).
It been a medium-to-high altitude bomb-truck and stand-off missile carrier.
As has the B-1B but it’s only just got back into the (conventional only) cruise missile carrier role. And the B-1B is not any more suited to a high altitude role than the B-52 (arguably it’s the B-1B that is substantially more tailored to the low altitude role).