ESP32c3 BLE5.0 PHY compatibility problem

[chase.chen]

Details of the problem:
Development environment: windows, IDF4.3, powershell
Software version: commit 88c2b69c68d3258d846c6e43f8cba329ccaa5898 (origin/release/v4.3)
Development version: esp-c3-12f-kit-v1.1
Example: examples\bluetooth\bluedroid\ble_50\ble50_security_server
examples\bluetooth\bluedroid\ble_50\ble50_security_client

History: The original ble50_security_server demo, using the old mobile phone honor9 (PS: Bluetooth 4.2, later represented by ble42Client) cannot search for the device;
Operation 1: Modify ext_adv_params_2M.type = ESP_BLE_GAP_SET_EXT_ADV_PROP_LEGACY_IND
Result: ble42Client can search and connect to the device normally;
ble50_security_client can also be linked to ble50_security_server_change;
But PHY_1M is used;

Expectation: ble50_security_client and ble50_security_server_ can be automatically switched to PHY_2M mode when the connection is changed;

Question: How to achieve it? Which API to use? In which process is it called? It's best to explain the process in detail. thanks;