Does this tax system help investors to save from froud?
Do you mean fraud?
When the market is taxed, that means it's regulated and the government will impose a penalty on those who are running a scam project. So most likely investors will be protected from fraud but it does not also mean that fraud will not happen.
Yes if people will follow only there government guidelines but considering this is crypto and most project is decentralized including exchange. There's always a time that investors might be unregulated since many project on crypto can be accessed easily via online. I believe government will just regulate the wallet transaction including exchange but those crypto that bought OTC will always be off the hook and free to trade without tax unless they cashout via regulated exchange.