You are right that you can use same wallet address for those 3 network since they are all came from ERC20 but you will not see the token from polygon network in your trust wallet unless you change your network via re-login which is very hassle on trust wallet. It's advisable to just use metamask for the convenience of change the blockchain network.
Trust wallet support multi chain like ERC-20, TRC20, BEP20, BEP2, Polygon, HECO. He can use BRC-20 wallet for BEP-20, HECO & Polygon. after received token just he have to add Custom token by token contract address. that's it