I'm of course angry mostly with Triumph, as you do. However, my dealer tried some things, can't deny that, but those were things I suggested myself and they just did it to shut my mouth, not because they shared my concern about the issue. Heck, they didn't even aknowledged I have an issue since I reported it immediately after I bought the bike 14 months ago. My first season experience is quite ruined by this, 'cause the bike spent like 3 months at the dealership (not just because of this issue, had more problems, most of them were known and sooner or later fixed, things like indicator malfunction, flawed heatshield etc.), but this one and the most concerning issue I have was there for the whole time, never recognized by them and actually when I tried to apply warranty claim for it, they declined with a statement that the bike does not manifest any odd behaviour. And that was without any measuring effort or any proof that the bike is ok.
So I guess it is understandable that I'm angry with them too now... Same argument as you said, I haven't bought 30G flagship bike to struggle from issue to issue and even face this "we can't analyze it so it must be ok" behaviour....