The changes only related to C6 and H2 chips where CONFIG_SOC_IEEE802154_SUPPORTED=y.
For this case these APIs return 8 bytes
esp_efuse_mac_get_default() -> 8 bytes
esp_efuse_mac_get_custom() -> 8 bytes
esp_read_mac(..., ESP_MAC_IEEE802154) -> 8 bytes
The rest cases len is 6 bytes