Relationship between "LE Secure Connections (LESC)" and Bluetooth version

Relationship between "LE Secure Connections (LESC)" and Bluetooth version

I am experimenting with the following contents.

・ "Central": iPhone 5s (Bluetooth v4.0)
・ "Peripheral": nRF52832 (SDK V15.3.0, S132 V6.1.1)
・ "Project": ble_app_multirole_lesc

I realize that "LESC" is a security introduced from Bluetooth v4.2.
Therefore, I thought that pairing by "LESC" was impossible in iPhone5s (Bluetooth v4.0).
However, when running the above project, it seems that it can be paired by "LESC".
Judged from the fact that the "lv4: 1" log was obtained in the "BLE_GAP_EVT_AUTH_STATUS" event.
Why are you able to pair by "LESC"?

The log is shown below.

<info> app: LE Secure Connections example started.
<info> app: Scanning
<info> app: [on_adv_evt] BLE_ADV_EVT_FAST
<info> app: Advertising
<info> app: [on_ble_evt] BLE_GAP_EVT_CONNECTED
<info> app: [on_ble_peripheral_evt] BLE_GAP_EVT_CONNECTED
<info> app: PERIPHERAL: BLE_GAP_EVT_SEC_PARAMS_REQUEST: bond=0x1, mitm=0x1, lesc=1, keypress=0x0, io_caps=0x4
<info> app: PERIPHERAL: BLE_GAP_EVT_SEC_PARAMS_REQUEST: oob=0x0, min_key_size=0x0, max_key_size=0x10, kdist_own=0x23, kdist_peer=0x3
<info> app: [on_ble_evt] BLE_GAP_EVT_LESC_DHKEY_REQUEST : PERIPHERAL
<info> nrf_ble_lesc: Calling sd_ble_gap_lesc_dhkey_reply on conn_handle: 1
<info> app: [on_ble_evt] BLE_GAP_EVT_PASSKEY_DISPLAY : PERIPHERAL : passkey=798260 match_req=1
<info> app: Press Button 1 to confirm, Button 2 to reject
<info> app: [bsp_event_handler] BSP_EVENT_KEY_0
<info> app: [num_comp_reply] Numeric Match. Conn handle: 1
<info> peer_manager_handler: Connection secured: role: Peripheral, conn_handle: 1, procedure: Bonding
<info> app: PERIPHERAL: BLE_GAP_EVT_AUTH_STATUS: error_src=0x0
<info> app: [on_ble_evt] BLE_GAP_EVT_AUTH_STATUS : PERIPHERAL : status=0x0 bond=0x1 lv4: 1 kdist_own:0x3 kdist_peer:0x2
<info> app: [on_adv_evt] BLE_ADV_EVT_FAST
<info> app: [on_ble_evt] BLE_GAP_EVT_DISCONNECTED
<info> app: [on_ble_peripheral_evt] BLE_GAP_EVT_DISCONNECTED : 0x13
<info> app: [on_ble_evt] BLE_GAP_EVT_CONNECTED
<info> app: [on_ble_peripheral_evt] BLE_GAP_EVT_CONNECTED
<info> peer_manager_handler: Connection secured: role: Peripheral, conn_handle: 1, procedure: Encryption