Ex CFIC instructor boom operator here. The maneuver wasn't to demonstrate operational limitations. It was (as another CFIC instructor in the article notes) a "confidence" maneuver. Many receiver pilots came to CFIC with the belief it is somehow more difficult to remain in contact while turning. The Whiff demonstrated that's simply not true. As long as the receiver pilot gets all their visual cues from the tanker and not the horizon, the BUFF doesn't really care what your bank angle is. On one mission we achieved 88 or 89 degrees of bank (the tanker and BUFF pilots couldn't agree on the precise number) without a disconnect. It was quite a view looking down and aft from the boom pod.

The Whiff was one of a list of air refueling demonstrations performed by CFIC instructors for their instructor candidates. One of my favorites was meant to demonstrate how much drag the boom imposes on the tanker. The two aircraft made contact after which the receiver would take time to fine tune the throttles to match the tanker speed as closely as possible--these guys were good, so the match was usually perfect. Once the throttles were set on both aircraft I would disconnect and fly the boom up to trail position. The reduction in drag would allow the tanker to accelerate and move away from the receiver. At a distance of 50' I would fly the boom down to around 40 degrees down elevation. The increase in drag would slow the tanker allowing the receiver to catch up. If I timed it right I could raise the boom at just the right time to make contact, and the two aircraft would again be at the same speed. The throttles on both aircraft remained set (unmoved) for the entire demonstration. The point of this demo was to drive home the fact that if a BUFF pilot allows his aircraft to get high or low in the air refueling envelope they will have to make a power correction.