Simon,
I could not find the Doohan statements. I did find in "Techniques of Motor Cycle Road Racing" by Kenny Roberts talking about developing his bike. He requested different seats, tanks, and engine changes for his bike. He changed them to suit his style.
For example, when Sheene was riding a similar Yamaha he told Roberts that the triple clamps were all wrong. Roberts said it worked for his style, rear steering, but not for Sheenes front steering style.
KR was injured for one race and Graeme Crosby test rode KR's bike for the race. It was unridable for Crosby and he was a good rider.
HRC wanted to win races. Doohan was best at time to do it. I would think that they give him what needed to win.
Being told that I am full of s### by Doohan would be OK with me.
Steve