Not quite which is where the hubris came in.
With Yamaha he correctly backed his talent without knowing what bike Yamaha would come up with but betting he could win on a Yamaha against one of the greatest bike designs of all time, the V5 990 Honda. I guess Yamaha did have some track record of success and it was not unexpected they could come up with something if they put full effort into a ground up design of a fit for purpose 990 MotoGP bike, but he went in sight unseen and very definitely proved to the Honda engineers he had something to do with the success of their bike.
The Ducati move was hubris, apart from being 8 years older he assumed if Casey Stoner could win on a Ducati he could win more, and that any latter day inconsistency was due to Casey being flaky or whatever. I also saw the famous Jeremy Burgess interview live on Australian TV, and while he didnāt really claim he could fix all issues with the bike immediately, he did say there were obvious things he and Valentino could fix in 60 seconds.
I didnāt have any real animus against Valentino back then, and said on this forum that if they couldnāt fix the bike then it was unfixable, but strongly doubted that they could.