Your question is a good one. The sample code I've seen out there has the and boolean logic linking max-device-width and the orientation.
What is driving me nuts is that I do not own a smartphone and therefore I am forced to use the so-called emulators whose effectiveness I've come to doubt .. in short, do they accurately emulate??
In addition, these emulators do not handle re-direction.
Bottom line .. I guess I really don't know if:
@media only screen and (max-device-width:480px) and (orientation
bombs on a real mobile phone .. it definitely does on 2 so-called iPhone emulators.
Many, many folk testify that the above @media works, but I just cannot confirm it.