No the armrest doesn't come as standard anymore I'm afraid.
We're trading in an old V70 XC AWD and a newer S60 and they both have rear armrests so I was really surprised to see that there wasn't one. They give you all these noncy-poncy gizmos as standard yet they don't provide an armrest!
As davek100 says, it's only a £35 optional extra at build.