FH1100
"How is it relevant?"
It's relevant because you said that no tilt-rotor/tilt-thrust/tilt-wing desgn had proved satisfactory. The design (and engineering) of the "84" was, by ALL accounts (including the US military), completely satisfactory. Most of the all-wise all-knowing (to borrow a phrase) decision makers of the time thought there was no need nor use for a "tilt-rotor/tilt-thrust/tilt-wing" aircraft. Perhaps others believed that US designers / engineers could do a better job.
Chill . . .
grizz