Comment by mjevans

I believe the implicit requirement is that the item is known to exist within the list. With that requirement in place the extra guards aren't requisite (they're implicit) and in kernel code this probably offers a performance edge and is a reasonable requirement. Either having an implementation that has an extra check once at the end of the list, or that verifies the presence of the item and passes that node through to a deletion subroutine, would be good alternatives but still utilize the same pointer to structure view.