Ms mia's personal Platinum card also has the Contactless feature, and also does not show the online option to order a metal card. Based on this sample of two I predict that you will receive another plastic card, with Contactless, and that the only way to switch to a metal card will be to call and opt out of Contactless. This seems to be further evidence that Contactless will not be available on the metal cards.
Sounds like the expected demand may have been too low to make it worthwhile to have a separate line just for metal contactless cards. I'd almost go as far as to say that contactless for US AmEx cards in general is only worth the trouble for them because of the aggregate demand across all of their cards; metal is apparently desired by consumers way more considering the posts here about them being "overwhelmed".