I am bit new to using voice on wireless. Should wmm ever be disabled?

Reading through Cisco doc Configure 802.11n on the WLC I found this:

"Note: Do not enable WMM mode if Cisco 7920 phones are used on your network. You cannot enable both WMM mode and client-controlled CAC mode on the same WLAN. When an AP-controlled CAC is enabled, the AP sends out a Cisco proprietary CAC Information Element (IE) and does not send out the standard QBSS IE."

But, when I read the Unified IP phone deployment guide it states:
“The WMM policy should be set to Required only if the Cisco Unified Wireless IP Phone 7921G or other WMM enabled phones will be using this SSID. If there are non-WMM clients existing in the WLAN, it is recommended to put those clients on another SSID / WLAN. If non-other WMM clients must utilize the same SSID as the Cisco Unified Wireless IP Phone 7921G, then ensure the WMM policy is set to Allowed.
"

My understanding is that if WMM isn’t allowed or required that 802.11n speeds will not be beaconed.

Any thoughts on this?

Thanks ~mocha