DHCP Options with Lync Phones, HP and Aastra

If I've got a Lync Phone - in this case I've tested with HP 4110, HP 4120 and Aastra 6725ip.

If the DHCP 02 Option is set to give a time offset of, say, 5 hours:

0xFFFFB9B0

I can see in the wireshark trace that the correct option/value is returned to the phone(s).

However, the phones always go with the Time Zone setting and ignore the DHCP information.

Is there a way to have the phones ignore the Time Zone setting and/or make it unset?

I can see of no way to make it heed the DHCP 02 Option information.