Note that using List<byte> as a workaround is not always possible e.g. where byte[] is being used for an entity Version property for Entity Framework optimistic concurrency checking. (See https://docs.microsoft.com/en-us/aspnet/mvc/overview/getting-started/getting-started-with-ef-using-mvc/handling-concurrency-with-the-entity-framework-in-an-asp-net-mvc-application)

Also, surely arrays are even more fundamental than Lists in terms of what should be supported for serialization?