Earlier quoted context omitted.
> my mental model is that ex-bourbon casks add basically no flavors other than the wood; I think of them as “neutrally casked“ Typically vanillas, nuts, toffees, woods, caramels, and some cereal notes (other cereal notes from the barley of course, which oak may not drown out as much as the fruitier sherries).
Those are all flavors you get when alcohol interacts with charred wood. They're not coming from the bourbon that originally filled the cask, unlike what happens with sherry.
Ah. I misread what you were talking about -- I though you were implying that the cask itself imparted no flavor for some reason. You were instead saying that with ex-bourbon casks, the previous spirit content imparts very little (if any) flavor. I agree!
From what I understand, Bourbon casks are also often re-conditioned and re-charred, which further supports this point.