Odd, says I. My 450HD just worked. So, I commenced to testing with the 405 and the 420HD that I happened to have handy. Here is my firmware load per phone:
I then proceeded to use the web interface on each handset to modify the login to the UPN of an SfB online user.
SfBO login with each model shown was successful. Note the firmware version per handset. Test calls worked. Transfer worked. Holds worked. All the basic features that I use worked just fine.
While the 405,420HD, and 450HD do not show on the SfBO OIP, they clearly function as expected.
Nice to know, eh?