I think it can go both ways.
Sure Rossi had to adapt to the Bridgestones, there was plenty of stuff at the time about how he had to change his riding style and bike set-up/front rear balance to incorporate elements of Stoner's style and set-up. This would mean Jorge who had spent his rookie year on Michelins and was rather competitive against Rossi in 2009 was disadvantaged btw.
It is more than possible that Bridgestone stopped specifically developing for Ducati for the 2008 season though imo, particularly with the control tyre coming in 2009, of which I somehow don't remember them being informed the day after the last race of the 2008 season. Certainly when a control tyre was about to be mandated Ducati said they would prefer to start again with Michelin rather than have a Bridgestone control tyre, and later, as early as 2010 iirc, publicly said that the control tyre was a significant reason why their bike no longer worked and that their woes could be resolved by a suitable tyre. There was also considerable talk in 2008 (admittedly substantially from Lex, another great former poster on here, I can't recall if he provided any links) that the complex asymmetric multi-surface tyre specifically co-developed by Bridgestone with Ducati was withdrawn in the 2008 season as a precursor to the control tyre.
I actually was the one who pointed out that there were no SNS tyres for the fly-away rounds in an earlier discussion, and also in this thread that there was talk, which I found credible, that Rossi thought Michelin were going away from him towards the end of the SNS tyre era (as a corollary this would mean that they had suited him more previously btw). It is a matter of historical fact however that HRC don't always get their way with tyres, cf the first riders' vote in 2012 (the 2017 vote being the second) which removed the tyre favored by HRC and Stoner, concerning which Nakamoto and Stoner complained fairly vociferously, Stoner correctly as it eventuated on durability/safety grounds.