The same is true for giraffes, which do not hold their necks
vertically (at least passively as extensively illustrated and
characterized for the bulk of sauropods).
I've often seen this asserted, to the point where it now seems
like orthodoxy. But whenver I see giraffes in a zoo, they are
standing with their necks near-vertical.
Mike, it might appear as "orthodoxy" to you when you see it
informally cited, but it is the result of scientific observations,
not just Sunday afternoon trips to the zoo. I point you to
(Leuthold and Leuthold, 1972; Pellew, 1984; Young and Isbell, 1991,
Woolnough du Toit, 2001).