I don’t know. It is an Air Force Photo.
I did take several myself at Eglin of an F-15 flying with two P-51s. I noticed the F-15 was pointed up a bit probably in order to maintain the slow speed.
Slow flight is only slightly faster than stall speed. Very unstable, control surfaces lose a lot of efficiency.
When the B-52 first became operational, the only aerial refuelers were KC-97’s or KB-29’s. Footage of a B-52 struggling to maintain contact with the fueling probe while not stalling out is hair raising to watch.
IMO the Boeing 707 was rushed into production in order to become the KC-135, which made refueling in flight for B-52’s a whole lot easier.