to be fair, in the linked thread @Jumhyn and i were disagreeing on precisely that: i felt that constraining
(JSONDecodable & RawRepresentable).RawValue:Sendable
made no sense, but he noted that the RawValue could easily end up in the payload of an error type thrown from a task inside a task group.
there is also the de-facto reality that in the absence of typed throws, Sendable “makes sense” almost everywhere.