Referring to the "Note a" in CYW43012 device datasheet page 1 and 2:
IEEE 802.11ac full-compliance requires support for 40 MHz and 80 MHz channel bandwidths. CYW43012 is 802.11acfriendly. It only supports 20 MHz channel bandwidth however it supports 802.11ac's 256-QAM for the 20 MHz channels in the 5 GHz band enabling it to offer higher throughput and lower energy per bit than 802.11n only products. In addition CYW43012, when used as a STA with an 802.11ac access point, supports 802.11ac's explicit beamformee feature to offer significantly higher throughputs than 802.11n chipsets at any given range.