Now your idea is much clearer to me.
The problem for these planes is the very large (negative) momentum coefficient of the high cambered airfoils combined with the torsional soft wing structure with very thin airfoils and soft wire bracing design.
This is a classical problem of static aeroelasticity. Increasing speed (or increasing dynamic pressure) the wing twists nose down at the wing tip producing an overall decrease in angle of incidence difference between wing and stabilizer. This is equal to a nose down elevator deflection and causes speed to increase even more.
So pulling out of a dive just lifts the fuselage nose but not the wingtip, making it imposible to end the dive.
About 10 Jears ago a test pilot was killed while doing high speed testing a composite microlight plane with the wing skin fibres orientated 0/90° (for cheaper production) which resulted in a far to low torsional stiffness of the wing. He was able to tell what was wrong with the plane on the radio until the very last moment, he had fully nose up deflected elevator but the plane dives steeper and steeper while the torsion of the wing became spectacular visible.
Might have been similar in the early WWI planes.