Interesting.
802.11ac's ("WiFi 5") core benefit was (with enough antennas) running channels on both 2.4GHz and 5GHz and supporting devices duplexing across both channels for maximum speed/latency shaping. It made running 2.4GHz cool again, and from what I'm aware of finally solved some of the compatibility issues between 802.11a/b/g and 802.11n so that there are fewer issues with older devices.
My impression from school ages ago is that though 802.11a botched the original plan and took years to fix while 802.11b captured the market, and 802.11n mostly fixed it right, and even though 2.4 GHz is one of the noisiest bands in the modern home (microwaves, old school walkie talkies/baby monitors, parts of Bluetooth, all sorts of other random home appliances), 2.4 GHz is still the technically superior band in a lot of cases, and WiFi frequency hopping and noise avoidance have gotten really good since 802.11a.
It's interesting me to decide to ban that entire band from one's home WiFi options.