a longer IR length is not always best for everyone in every circumstance - Fractal has also said: "FWIW, I almost always reduce IR length on my personal presets. Usually 512 or 1024. I like the lack of reflections".
I also still think the level of difference people hear is often exaggerated in relation to other factors as with tube type discussions, tonewoods ... it's there, but it starts getting into the hair splitting zones that many can barely hear or not at all. For those that can hear it and want it as an option, then ya, I guess it's a benefit of legacy IRs not yet in dynacab
Oh I can hear the difference. But then there was the day I had a few beers and was blasting away on some preset. And I thought it sounded good, and it was a good time. Then I found I had inadvertently switched cab channels and it was on the default IR. Pignose maybe? Something like that anyway.