It's a confusing photo; those antennae are for that machine as a client, not an access point. I use it only as a router (i.e., it routes my LAN to the internet over gigabit fiber), and I use a separate access point for wifi.

The antennae are useless for my use case, but they came with it and if I removed them I'd just have to find somewhere else to store them...

Intel WiFi chips work as acess points only in the 2.4 GHz band. You can add an "Alfa Network AWUS036ACM" USB WiFi adapter as something that works in the 5 GHz band, but please don't expect more than 400 Mbps from it.

They are not really limited to 2.4 GHz band. All recent Intel chips have a stupid mechanism built into the firmware: instead of getting the country code from the OS, as everything else does, and then follow the local spectrum regulations, the chip tries to discover it automatically. Tries, because it's half-broken and most of the times it fails and locks the radio to just a few 2.4 GHz channels with ridicolous power limitation (the LCD of all countries laws).

It's supposed to perform a scan and then set the country that is advertised by nearby APs. The obvious problem is that it won't work if there are no other wifi networks, or if one is trasmitting the wrong country. Also you have to manually run the scan, before the radio is unlocked, but virtually all AP softwares don't know how to handle this properly and get stuck in a loop.

In any case, they're terrible in AP mode even after unlocking the 5GHz band, because are locked to a single VAP and are not dual-band (I mean, not at same time).