It still doesn't make any sense at all.
Let's do a littel math to see what he implied by saying,
"In the flight's final seconds, the plane climbed at three times its previous rate — from 3,960 meters (1,200 feet) per minute to 11,220 meters (3,400 feet) per minute."
3960 feet per minute = 66 feet per second
11200 feet per minute = 187 feet per second
The cruise speed for 747 is 850 feet per second (Mach 0.85)
So roughly the increase in the velocity vevtor was 187 ft/s minus 66 ft/s = 119 ft/s.
In how long time? The article said "In the flight's final seconds". Let's assume it amde it in 3 seconds.
Therefore the acceleration rate is 119 divided by 3 = 40 ft /s2, about as much as 1.25 "G" (32.15 ft/s2).
It's not a big deal for 747 and I believe it has no problem to sustain 1.25 "G".