Using a wireless charging holder while your phone is connected to a USB-C cable should generally be safe. Modern smartphones are designed to handle multiple charging methods simultaneously. When a phone is connected to a wired charger, it will typically prioritize that charging source over wireless charging.
Regarding your concern about the phone's receptacle wearing out, it's true that constant plugging and unplugging can contribute to wear and tear. If vital functions are transmitted through Bluetooth, and you can manage short trips without using the wired connection, it might be a reasonable strategy to reduce wear on the phone's charging port.