Agreed for non-resilient libraries/code, but for evolution-enabled libraries where there’s no specialization this can give pretty awful performance. I know there’s the withContiguousStorageIfAvailable thing which mitigates this, but that can be easy to forget and also can fallback to really bad performance when not available/used.
Though maybe this won’t be nearly as much of a problem with the future sequence types given the design direction of having them vend the concrete [Mutable]Span types as their currency as noted here SE-0516: Borrowing Sequence - #9 by ben-cohen