ERC20InterfaceUpgaradable.sol

Important changes to the ERC20 implementation

ERC20Interface will be using the balance info coming from gAVAX, so there is no _balances

    /**
     * @dev gAVAX ERC20 interface doesn't use balance info, catches it from ERC1155.
     * mapping(address => uint256) private _balances;
    **/ 
    function _transfer(...) internal virtual {
        ...
        unchecked {
            _ERC1155.safeTransferFrom(sender,recipient,_id,amount,"0x00");
        }
        ...
    }

There is also a function for pricePerShare, so it is easy for any code to keep track of underlying AVAX balances.

function pricePerShare() public view returns(uint){
            return _ERC1155.pricePerShare(_id);
    }

Balance info for the used ID's ERC20interface will show the gAVAX balance info.

function balanceOf(address account) public view virtual override returns (uint256) {
        return _ERC1155.balanceOf(account,_id);
    }

TotalSupply info for the used ID's ERC20interface will show the gAVAX totalSupply info.

    /**
     * @dev gAVAX ERC20 interface doesn't use totalSupply info, catches it from ERC1155.
     * uint256 private _totalSupply;
    **/ 
    function totalSupply() public view virtual override returns (uint256) {
        return _ERC1155.totalSupply(_id);
    }

Note, these code pieces should NOT be used in production.

See it on Diffchecker.

See it on Github.