Where does wpa_supplicant get WPS-PBC-ACTIVE?

Setting up a hotspot on Ubuntu 20.04 server. The wireless card is Qualcomm Atheros AR928X. Setup with Netplan and the AP works. But I would like to disable the WPS and only keep WPA-PSK part. The netplan script is:

version: 2
     renderer: NetworkManager
     wifis:
       wlp2s0:
        dhcp4: true
        optional: true
        access-points:
          "my-ap":
            password: "mypassword"
            mode: ap

Tried several ways and found some clue from wpa_supplicant. According to the wpa_supplicant log:

...
systemd: Starting WPA supplicant...
wpa_supplicant: Successfully initialized wpa_supplicant
systemd: Started WPA supplicant.
wpa_supplicant: wlp2s0: CTRL-EVENT-REGDOM-CHANGE init=BEACON_HINT type=UNKNOWN
wpa_supplicant: rfkill: WLAN soft blocked
wpa_supplicant: nl80211: deinit ifname=wlp2s0 disabled_11b_rates=0
wpa_supplicant: wlp2s0: WPS-PBC-ACTIVE
wpa_supplicant: wlp2s0: SME: Trying to authenticate with 5c:02:14:75:7d:33 (SSID='hoho' freq=5200 MHz)
wpa_supplicant: wlp2s0: Trying to associate with 5c:02:14:75:7d:33 (SSID='hoho' freq=5200 MHz)
wpa_supplicant: wlp2s0: Associated with 5c:02:14:75:7d:33
wpa_supplicant: wlp2s0: CTRL-EVENT-SUBNET-STATUS-UPDATE status=0
wpa_supplicant: wlp2s0: CTRL-EVENT-REGDOM-CHANGE init=COUNTRY_IE type=COUNTRY alpha2=CN
wpa_supplicant: wlp2s0: WPA: Key negotiation completed with 5c:02:14:75:7d:33 [PTK=CCMP GTK=CCMP]
wpa_supplicant: wlp2s0: CTRL-EVENT-CONNECTED - Connection to 5c:02:14:75:7d:33 completed [id=0 id_str=]
wpa_supplicant: wlp2s0: CTRL-EVENT-SIGNAL-CHANGE above=1 signal=-63 noise=-95 txrate=13000
wpa_supplicant: wlp2s0: CTRL-EVENT-SIGNAL-CHANGE above=1 signal=-57 noise=-95 txrate=121500
...

Not sure where wpa_supplicant get the "WPS-PBC-ACTIVE" parameter, read from the wireless adapter or its own configuration file (there is no /etc/wpa_supplicantl.conf file through). How can I find this parameter and disable it?